Grunfeld or King's Indian??

Who said anything about amatuer players? 

I've completely ditched theory by move 9 in the KID twice in tournaments (in the same line funnily enough because it had worked out well for me the first time), and that's how I scored my 2 highest rated wins (2410 uscf and 2275 uscf). Some lines get very tactical, even nonbook ones, and whoever understands the position better will win. But still knowing theory will win you games, it has for me before in the KID.

ABSOLUTELY NOT!

You could "remember" all you want, but if you don't actually UNDERSTAND all the moves, it won't do you jack because you'll be clueless about what to do when your opponent deviates on you!

Your game won't be worth sh*t if you rely solely on memorization.  I'm a 2100 player.  I've deviated from the books many times ranging from moves 7 thru 20 in various openings.  If all everybody did was follow books to the end, the result would be known from the beginning.

My openings of choice (1.e4, Najdorf and Taimanov, Grunfeld and Dutch) is because I actually understand them.  There are others I truyly understand (i.e. Slav, Orthodox QGD, King's Indian Defense, etc), but they just aren't my style of play.  As for openings I don't really understand fully (Nimzo-Indian, Modern Benoni, Queen's Gambit Accepted, etc) I could try to "memorize" them, but that won't do me much good.  If the opponent deviates, why is the deviation inferior?  Is it clearly inferior?  Or a "+0.18" move vs a "+0.21" move?  If he stays in book the whole way, what happened if he really does "outbook" me?  This is why understanding is critical, not rote memorization.

I like to play the KID too it's extremely tensed and positional opening, I would suggest if you like an explosive position this isn't the opening for you. That dark square fianchetto Bishop becomes like a monstrous dragon after the centre opens up and it's extremely fun to attack from the side your king is castled on. I like to play really positional and closed position hence this is my favourite opening. But I have a question if 1. d4  Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6 5. Be2 e5 6. Bg5 O-O 7. d×e5 d×e5 8. Q×d8 R×d8 after exchanging queens does the position becomes boring and does black loses all it's attacking chances after exchanging Queens? The line mentioned above does not go well with the theory after White's Bg5 move c5 is the correct move ig. The point is I just wanted to give a line where Queen's are exchanged off the board.

This thread is about 11 years old now but I felt that I could add something since I've studied both KID and Grunfeld. The theory in KID is no joke, there's a reason why Kotronias wrote 5 volumes (totalling at just over 2300 pages) just purely on that opening. 

Playing it at even a club level requires you to know rudimentary theory of mar del plata, samisch, four pawns, averbakh, classical (petrosian, gligoric, exchange etc), fianchetto and others. And most of them are fairly theoretical, meaning you can't really make up a move on the spot. 

KID has an exorbitant amount of theory, which Bologan and Avrukh condensed well. 

Grunfeld however, certainly has lesser, you'll need to learn the exchange, classical, and also the neo-grunfeld to prepare for a possible catalan vs grunfeld, which is also playable.

I was also going through the same question and I came across this post I was a kid player for long time when I started chess I also purchased gm  gawain Jones free course on kid on chessable which was truly awesome 

But i am also a complete d4 player and after fm Daniel barrish course on d4 i have alway smashed kid with the samisch system and i play catalan and playing the same fianchetto setup with more space and a good long diagonal bishop is better 

That's why nowadays I prefer going d5 and c5 gruenfeld defense and anyway I think the modern chess engine has complete ended the supreme reign of kid with the variations like samisch, bayonet and makaganov 

So now I was more interested in gruenfeld that's why I brought swidler course on gruenfeld which is also completely fabulous 😋✨

And I would suggest to prefer grunfeld instead of kid but if you r anyway interested in kid like me after seeing games of great garry kasparov and Bobby fischer  and hikaru kindly checkout gm gawain Jones course on chessable

And yes many of us have started playing the kid after getting fascinated by mar del plata variation personnel experience, you will rarely see anyone play into mar del plata system not only in intermediate or advance but even title players nowadays will take you into the other mainlines like saemisch, bayonet, makaganov, London, trompowsky, or some kind of fianchetto systems as this lines gives more assurance to white to get an edge and if you play the kid the stockfish will  already start showing +2/3 in first 10to 15 moves and most of time you will find yourself defending a kingside attack

Grünfeld Indian Defence is more sound. It was played 5 times at the Yekaterinburg Candidates' to 5 draws. King's Indian Defence is dubious. Kasparov and Radjabov gave up on it.

Exactly kasparov gave up on kid after his many losses to kramnik