A is faster. Both use Shunshin which speed depends on chakra reserve and chakra control. A has Bijuu level chakra and his lightning armor allows his synapses to fire like a flash of light in lvl 1 lightning armor so imagine level 2. Gai used gates 5-7 against weakened Kage level+ enemies which isn't really an impressive feat.
Against Kisame's 70% clone who made 3 water clones which made the Kisame Gai fought at 5th and 6th gate was at 17.5% power. The last time they fought is when Kisame was weakened after being hidden inside Samehada for days and didn't have Samehada to fuse. Bee is faster than 7th gate Gai, he was moving too fast for Sasuke only in 3 tails version 1 which required Karin to keep track of Bee for Sasuke.