depends on his play vs. 4bs
if he is well-adjusted vs. 4bs and is very robust preflop a 4b is better because he'll jam Ax and 22+ as semi-bluffs
but most people 3b tons and don't adjust their felting ranges so they'll only shove QQ+,AK for value and won't really shove bluffs which means a 4b with trash is awesome until they figure out what you're doing

that said, his bet sizing on flop/turn means he's going for all three streets with half pot bets
whether he's trying to get you off like 88 or he has Kx/KK+ I don't know, it's a good line on dry boards