Which one is better?
Never really got intention to grind out La-7B-20 to compare it to regular La-7. Its only real difference is Shvaks being replaced with B-20s, ammunition per gun got reduced (one more gun added) and fire rate is quicker.
Basically what this means you have punchier gun loadout (3 faster firing autocannons vs 2 less fast firing autocannons) with downside of this change being even smaller ammunition per gun, which will hit you even harder if you really cant keep look out for ammo.
I would say if ammo management and aiming isnt a problem La-7B-20 is better, but at same time not as much as it may seem.
If you re looking if its so much better that you must make sure you play it a lot than I wont advice it, regular La-7 is already good with Shvaks, difference in armarment is not really worth it to grind out modifications from zero again (My opinion).
If you’re looking at a good prop plane to play La 7s are generally good. Just gotta know the playstyle, playstyle is a key to playing vehicles and winning encounters.
5.0 (La-7B) is a terrible BR where you get a lot of up-tiers to 6.0 with JU288s.
You’re also trading a noticeable amount of flight performance for an extra gun with less ammo. (130 per gun instead of 170).