Hard to say. I think on a one punch basis, Walcott's hook was a bit harder than anything Tunney had, however Tunney had a harder right hand, harderer body shots, and seemed to throw more punches in general.
This seems a reasonable summary. Just to add though, that Walcott looked the trickier of the two, and although Tunney's punches are far from telegraphed, Walcott's look harder to pick off.
Lets not blow Tunney out of all proportion here. Louis would be a whole new ball game compared to anything he ever went up against. Two wins over a shell of Jack Dempsey dont prepare him for this. Sure he could win but god help him if there was ever a rematch.