Will 1IV short of 31 make a huge difference in battling?

>>30937773
in speed, yes
in anything else, doubtful

>>30937773
Only in speed

>>30937828
Well my pokemon already has 4 IV's in speed so I'm bottle capping that

Huge difference no (unless it's speed). Enough of a difference that you should care if you're seriously trying to win: yes. Of course you can just hyper train :^)

>>30937773
Only if it's in speed and it's not nearly a *huge* difference. You used to have to do this all the time for desirable hidden powers.