mista lowkey stomps, outranges hard (Act 1 has 10m firing range, Sex Pistols is like 5x that at least), faster, has way more ammo (johnny has 20 shots maximum and must wait a bit for the nails to regen), sex pistols might be able to deflect the bullets and even if they cant, mista can just dodge while johnny, due to being johnny, cant dodge shit and even if he could sex pistols just does what sex pistols does best
I don't think Johnny has any advantage here tbh except maybe raw AP, but that doesnt matter given Mista is one shotting him too given he aims for the head, and johnny missing and blowing off his arm wont kill him, assuming it hits.