I used to play the QGA but recently I switched to the tarrasch / semi tarrasch. So far I'm pretty happy with the tarrasch, players seem to not know how to respond to it, and it's not commonly played. People avoid it cuz they don't like IQP positions but the opening is completely legitimate and puts alot of pressure on white.
++ Personally not a Tarrasch fan as Black. Perfectly reputable, but the Tarrasch isn't hard to book against if your opponent knows it's coming, and White very often gets to choose the variation and some of them aren't fun to play against.
QGA is nice if you want a viable attacking opening that takes control of the game early, minimizing the theory you must learn.
++ It works practically but from a principled perspective it's terrible. It's up there with the Caro-Kann and Grunfeld for me on the 'why does it work?' scale. That being said the mainline isn't fun for Black at all, White just gets normal classical QGD stuff without having to worry as much about key tension breaks in the center.
Slav gambits / benko gambit are also very good attacking options... though there are more ways of white avoiding these lines so you'll need to learn more theory. Slav gambits are considered completely solid at the GM level though.
++ I'm assuming by Slav gambits you mean the normal Slav lines... if not, then ignore this. Slav is fun, one of my favorite Black defenses against d4. Love the aggression, love the simplicity, it feels like a Sicilian merged with a QGA in the best way possible.
Benko Gambit... I actively dislike as Black. White has far too much play in anything but the Fully-Accepted, and even there I much prefer White's positions. I much prefer the Blumenfeld Countergambit. Simple, relatively sound, incredible fun, easy to add to a c5-Nimzo/Benoni repertoire, all while being incredibly aggressive and counterattacking, what's not to love?
Semi-slav is cool but it's too much theory and too common for my tastes.
++ Which one? I've literally never managed to get someone to play a Meran as either side, but I play a crap ton of Botvinniks (as White. Over my dead body will I allow a Botvinnik, I'll take on c4 on MY terms, thank you very much). If the Slav is the Sicilian QGA, then the Semi-Slav is the Ruy Lopez QGA, the simple complexity, the positional tactics, the minefield of thinly-veiled aggression from both sides. Love it to death. Theory is a valid friction point, but if you can do Tarrasch you can do Semi-Slav.
English defense is also a good attacking alternative to the NID, though you should pair it with the QID and the french and enter it via 1... e6. Really this only makes sense if you play the french vs 1. e4, but if you do it's a great line.
++ English is fine. That being said, it's just a b6-NID/QID repertoire with way more steps and things to know. Like, an insane amount more. Also, yeah, having to play the French is a friction point, but not insurmountable, as one could run a reasonable Fort Knox/Bd6-Ne7 Exchange/Wade Advance repertoire up to a certain point at the club level alongside their regular repertoire, as those play so intuitively from the Black side.
KID / NID are too typical / predictable to be a good choice at club level, plus the KID is very unforgiving and NID is too gigantic.
++ KID is pretty unforgiving, but avoid the Mar del Plata and you have counterplay in every other variation. It isn't personally my favorite, I tend to like keeping my options open, but you really can't do that in the KID, you usually only have one viable option according to the engine, and that just isn't my style. That being said, it isn't too bad, and it is perfectly sound and for French players this should be a real consideration.
Calling NID gigantic is technically correct but also blatantly false. As White, you pick one of 5 lines and only learn that line's 5 responses. As Black, you learn one of 5 responses for each of the 5 lines. Sure, there are 25 rich, deep lines to study, but you can completely ignore 20 of them, just like in any opening. Alternatively, you can learn 0 and play it based on feel, which also works due to how solid and flexible the opening, something that very very few openings accomplish. Also, the BID is piss-easy to play, super flexible, and ultra-solid, all while covering both good anti-nimzos.
Grunfeld is also not recommended at lower levels for the same reasons - unforgiving / gigantic amount of theory required.
++ I kind of agree, but not fully. There's a decent amount to learn, and it also requires a very specific type of player. I took to it like a duck to water, but then again I'm a very unconventional player. However, the fact that Black has such a good setup so early on means that White either settles for a less-than-perfect setup which is exploitable longterm or tries to push his luck in the Russian or Exchange. Anything goes in the Russian, good luck prepping it, but the Exchange is usually quite tame and Black always has the killswitch of trading everything down to a drawn endgame.
Benoni is generally just not hard to play against and you should find something else.
++ Disagree. Benoni is as good as the KID, both of which are only slightly worse than the Grunfeld. Ironically, I'd say this pairs extremely well with the Caro-Kann. Both play in a very anti-principled manner to achieve a cramped but rock-solid position that can wreak havoc if it survives the intense middlegames which will inevitably arise. Philidor players also rejoice.
Dutch is also pretty easy to rip apart.
++ Full disclosure that I literally have no clue about anything pertaining to the Leningrad, I've never played either side of it and I haven't looked into it at all, and nobody talks about it, so this segment will be exclusively about the e6 Dutch.
It may be sound, but it's hanging by a thread if it is. I score well against it, GMs don't play it, it scores really poorly, engines don't really like it, but there are a few people who swear by it and it doesn't have glaring weaknesses, it just also doesn't have any strengths, like at all.
The black lion defense also looks interesting, I haven't played it myself but winrates are very good and some people swear by it.
++ I'm assuming you mean 1... d6 2. e4 Nf6 3. Nc3 Nbd7? It's okay. If you can manage the incredibly limited space you have well enough, I might even call it sound. Combine it with the Rat Defense with 1... d6 2. d4 e5 (offering a very advantageous queen trade or a much better KID structure) and you have one FUNKY FRESH repertoire. That being said, the 2. Nf3 3. c4 players will be able to avoid both of those, so add Tiger's Modern (a6 d6 g6 Bg7 b5 Bb7 being the defining structure, with c5, e5, d5, and f5 all as viable pawn breaks depending on what White does, flexibility is the name of the game here) to your repertoire for a completely legitimate repertoire somehow featuring three animal-themed openings that hardly anyone plays. That being said, play this repertoire at tournaments and you may just find out why hardly anyone plays these.
Not mentioned above are the Modern (which is good if you like flexibility and hate theory), the Budapest, Chigorin, and Baltic, (which are all unsound, but perhaps playable below 2000 with some good fundamentals and prep), and the big one:
The QGD (Fantastic, I recommend a repertoire like so: 3. Nf3 Bb4+ is really good, there's no known theory after 4. Nbd2 dxc4 but Black does really well, you transpose to the Ragozin after 4. Nc3 Nf6 and the Ragozin is really really good, and after 4. Bd2 Be7 5. Nc3 Nf6 the game will either transpose to a Classical QGD or a Harrwitz which are both good for Black. Play the Ragozin with 3. Nc3 Bb4, and play the Catalan with 3. g3 Bb4+ 4. Bd2 Be7 5. Bg2 Nf6 6. Nf3)
The Classical QGD lines are fantastic, the Lasker, the Tartakower, the Mainline Orthodox, the Rubinstein, the Mainline Neo-Orthodox, the Cambridge Springs, et cetera ad infinitum.
The Ragozin is phenomenal, as I mentioned above.
The Vienna is great, albeit very sharp in many variations and it requires cooperation from White.
And I think that's all of them!
I used to play the QGA but recently I switched to the tarrasch / semi tarrasch. So far I'm pretty happy with the tarrasch, players seem to not know how to respond to it, and it's not commonly played. People avoid it cuz they don't like IQP positions but the opening is completely legitimate and puts alot of pressure on white.
QGA is nice if you want a viable attacking opening that takes control of the game early, minimizing the theory you must learn.
Slav gambits / benko gambit are also very good attacking options... though there are more ways of white avoiding these lines so you'll need to learn more theory. Slav gambits are considered completely solid at the GM level though.
Semi-slav is cool but it's too much theory and too common for my tastes.
English defense is also a good attacking alternative to the NID, though you should pair it with the QID and the french and enter it via 1... e6. Really this only makes sense if you play the french vs 1. e4, but if you do it's a great line.
KID / NID are too typical / predictable to be a good choice at club level, plus the KID is very unforgiving and NID is too gigantic.
Grunfeld is also not recommended at lower levels for the same reasons - unforgiving / gigantic amount of theory required.
Benoni is generally just not hard to play against and you should find something else. Dutch is also pretty easy to rip apart.
The black lion defense also looks interesting, I haven't played it myself but winrates are very good and some people swear by it.