For grins let's look at the same thing for barbarian at 8th level. I played with the numbers and the best way for A to increase damage is polearm master and a Halberd, assuming they'd get to use bonus action attack 4/5 of the time.
Average damage per turn for B is 83% higher per turn.
But wait - there's more!
A: HP: 69, AC 12 (15 with breastplate), Initiative +1, Perception +2, Stealth +4, Survival +2
B: HP: 93, AC 17 (no armor), Initiative +3, Perception +4, Stealth +6, Survival +4
PC A isn't even in the ballpark and will never catch up to B.
In any case if I have an error in my damage per turn estimate let me know. But we aren't talking the different between a +3 and a +4. But even that is around a 14-16% difference if using the same weapons. It's not just a difference in chance to hit we have to take into consideration average damage from the weapon plus strength modifier times the %chance to hit.
Average damage per turn for B is 83% higher per turn.
But wait - there's more!
A: HP: 69, AC 12 (15 with breastplate), Initiative +1, Perception +2, Stealth +4, Survival +2
B: HP: 93, AC 17 (no armor), Initiative +3, Perception +4, Stealth +6, Survival +4
PC A isn't even in the ballpark and will never catch up to B.
In any case if I have an error in my damage per turn estimate let me know. But we aren't talking the different between a +3 and a +4. But even that is around a 14-16% difference if using the same weapons. It's not just a difference in chance to hit we have to take into consideration average damage from the weapon plus strength modifier times the %chance to hit.

