It really depends on the roads you ride on. I'm fine with 32mm on my bikes for the roads I normally ride on. But, I did a 3 day tour from Venice FL to Jacksonville and on the advice of locals I put on my 35mm Schwalbe Marathons. There were several stretches of long highway "shoulder" that were basically like driving through a automobile junkyard. I don't know if the 32mms would have flatted but the 35s got a bit gouged (which I rarely have happen up here) and picked up radial shards without flatting.
But outside of that ride, I'm staying with 32mm.