cuz you prepare h5
Can someone explain why g4 is better than h4 here?

This is a very old line that has been considered better for White for years. Whites idea is g5 followed by Nd5. 14... b5, sacrificing a pawn for active play is accepted as best here. After 10 Bb3, ...Nxd4 is the simplest way to avoid the g4 idea. Hope that helps.
Both moves g4 and h4 are viable. Nobody and not even the engines know for sure which one is better if one is better than the other at all.

This is a very old line that has been considered better for White for years. Whites idea is g5 followed by Nd5. 14... b5, sacrificing a pawn for active play is accepted as best here. After 10 Bb3, ...Nxd4 is the simplest way to avoid the g4 idea. Hope that helps.
Thanks

In the dragon, opening the lines to the enemy king is very important. And this can be done best by playing h4 h5, opening the h5 file. But at this position, the most played, and the best move by the engine is g4. Why, and how is g4 better than h4?
I have the answer.
When you play h4 black can simply play h5 and you won't be able to break through. But when you start with g4 you will be able 1 move later play h4 and there won't be h5 due to gxh4 and you would open g file to attack black's king Yes, black can also take with the knight but it will stand here forever and do nothing or you will have a new line of attack. g4 generally puts on much more pressure on the opponent
Hope it helps Levent If you have more questions lmk
Actually I have 100% as black in c.c. games after ...h5 and retaking with the Knight! It's not so bad for Black as it looks at first sight. or, at least, none of my opponents managed to refute it. All part of the fun of playing the dragon!! Everyone should try it.

The h pawn should advance first. By you have to start by g4 because on h4 there would be h5. So the plan is g4 then h4 then h5, then if they take on h4 you play g5 kick the knight and R:h5

the answer is pretty obvious. after black plays h5, i don't see how you can play g4.
I could call it lack of fantasy. Actually g4 can be played straight after 14.h4 h5, with a very sharp game where the one with better home preparation wins. Here ia a game (the move order is different, but the actual position is identical).
But I think g4 is more to the point, and more natural to handle.
The position at move 16 there was theoretically critical at one time, and can arise via various different move orders.
In the dragon, opening the lines to the enemy king is very important. And this can be done best by playing h4 h5, opening the h5 file. But at this position, the most played, and the best move by the engine is g4. Why, and how is g4 better than h4?