What are the differences between b4 and b3 openings !?

I always play b4 so I wouldn't know much about b3 , but quick glance at b3 early middle game gives me feeling like I'm playing b4 , looks similar. 

I'm sure there are not the same openings all together, but what are differences?  

In a chess world Larsen opening gets more credit and respect, then Sokolsky is there so much differences?  From b3 to b4 ? 

Anyone else want to contribute to this forum? 

#1
b4 leaves 2 holes at c4 and a4, but allows to chase Nc6 with b5
AlphaZero ranks b3 above b4, see figure 31
https://arxiv.org/pdf/2111.09259.pdf
Fischer played 1 b4 in some simuls, but not in serious play.
https://www.chessgames.com/perl/chessgame?gid=1255196 
Fischer played 1 b3 4 times in serious games and won all 4.
https://www.chessgames.com/perl/chessgame?gid=1044318 

Very interesting, thank you for the information.

Besides just two holes it would be interesting to know, why alpha zero chose b3 over b4 and same with Fisher , must be some other reasons as well

#4
"why alpha zero chose b3 over b4 and same with Fisher"
++ The 2 holes are reason enough. Nb8-d7-b6-c4/a4 strikes at Bb2.
b3 supports c4.

An immediate b4 creates weaknesses, as the c4 square no longer has reliable pawn protection.  The d-pawn is the only pawn that can then cover it, but the d-pawn usually wants to go to d4 in many openings that are not "English Opening" type setups (this setup includes the Closed Sicilian), or King's Indian Attack, etc.  Also, playing an immediate b4 costs a tempo as this pawn is unguarded on this square and another move must be spent to protect it.  It also gives Black information as to what you're doing immediately, so he can set up a suitable defense and fight for equality.  b4 tends to be more effective when played a bit later, especially in some gambit type positions (e.g. b4 ...cxb4 a3) where Black has a pawn on c5, and Black has a structure like h7/g6/f7/e6, or if White can get in b4 favorably (e.g. without loss of tempo).  So basically, it restricts White's opening possibilities as he doesn't want to allow Black to gain solid control of c4.

An early b4 is actually one of the main lines in the "symmetrical" English opening, especially when Black has committed to the ...g6 and ...e6 setups and has already played ...Bf8-g7.

One unusual response to the Reti runs 1. Nf3 b5. Black with less oomph from the opening anyhow, tries to put some Q-side cramping on White, who is likely to try a K-side fianchetto.

1.b4 isn't a terribly reliable opening- white has some trouble in the main line with 2...Bxb4.

1.b3 is certainly a better try, although I would probably consider starting with 1.Nf3 first, and then 2.b3.

I'm not too familiar with 1.b4, is this line just equal but uncomfortable for white, or is black actually getting a small advantage in the main lines of the polish?

No, it leaves holes on a4 and a3. Time to work on your positional basics 

More importantly, IMO, is that basically learning a single line black can easily equalize... so can just learn it and forget about it since you'll only face it once in 1000 games.

So doesn't seem like a reasonable white choice... if you're going to surprise your opponent, make it something dangerous or at least something that will force them to remember a lot.

Can pretty much ignore what white's doing and play all these moves to get equality.

Start thinking a little after move 8.

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Agree with this. Which is what I try to do with my pet 1.Nc3. Black can try to equalise in 4 or 5 different ways, but there are always tricks and I feel white's position is always more fun and easy to play for humans, even in the absolute most critical lines. Believe it or not this line is one of the very best ways for black to play against my pet line, the final position is somewhat unclear. And yet I've had titled opponents just resign the game after this sequence appears on the board because they wrongly assume they're lost.

There are different types of equal positions though. If black can just remember a few moves and equalise with no risk against 1.b4, then I agree it's rubbish (at least from a practical standpoint). But as you point out, black only faces this 1 in 1000 times, so if white has far more experience in the equal middlegames that come out of 1.b4, then his chances of outplaying black are probably good.

It is in no way uncomfortable for White.

Both 1.b3 and 1.b4 are dead equal.  The reason no GMs play either as their main weapon is it lacks the slight advantage White gets with 1.e4, 1.d4, 1.c4, or 1.Nf3.

1.e4 leaves holes at d4 and f4.

1.d4 leaves holes at c4 and e4.

The "holes" you guys claim is not the issue.  It is the lack of claim of the center.

1.b3 e5 2.Bb2 Nc6 3.e3 d5 4.Bb5 Bd6 5.f4 Qh4+ 6.g3 Qe7 7.Nf3 f6 8.fxe5 fxe5 9.Bxc6+ bxc6 10.Nxe5 Nf6 11.Nxc6 Qe4 12.O-O and 1.b4 e5 2.Bb2 Bxb4 3.Bxe5 Nf6 4.c4 O-O 5.a3 Ba5 6.Nf3 Re8 7.e3 d5 8.cxd5 Nxd5 9 Be2 are both equal.

And c4 is rarely a "hole" because e3 opens the Bishop to play c4.  Many lines also see a2-a4 played by White.  Especially 1...d5 libes and KID setups by Black.

Wow so many strong and knowledgeable players comment on this ! I'm learning a lot and I think it's useful for others too.

White usually gains a space advantage in the queenside in almost all lines but the bxb4 line with b4. He has to waste a tempo pushing or defending the b-pawn though.

b3 is more modest in space and more flexible.

If black is pressed, white will be forced on some narrower corridors with 1.b4 but its otherwise equal.  But b3 is not that great a try for opening advantage either to be fair. You play both to get interesting games not to keep first move advantage for us long as possible. 

I play both but prefer 1.b4 for must win games agaisnt stronger players. 

I see.

I knew 1.b3 was just equal, but the way pfren wrote about 1.b4 led me to belive that white might be slightly worse with best play. Thankyou

the line that seems to have the unclear assestment is 1.b4 e5 2.bb2 bxb4 3.bxb4 nf6 where the big debate is whether this is slightly better for black, white or equal.  For the longest time, as per sokolsky's assestment 4.c4 was believed best ( or 5.c4, point being black should not be allowed to get the d5-c5 duo or he is slightly better already) but with the help of engines , the line is somewhere between slightly better for black or dead equal. More concerning is that some of engine lines are very forcing  which means you can fall for black's preparation.

but in the last few years 4.c3! has been recommended by the engines,and Carlsen has popularized this by getting good games vs Giri and Nakamura with it. white plays on the dark squares playing for d4 and hoping for bxf6 (before black can play nd7), and play for e3 , g3, bg2, ne2  kind of stuff. This seems confortably equal although they are a few move order tricks white must watch out for involving qa5 ,re8 and/or bg4 ideas.

solid b3, aggressive b4.

3.a3 is objectively better than the gambit line 3.e4, although if you well prepared, the likelyhood of a knockout in that line is fairly high.