The sizing is the same, but I find the 333s ever so slightly narrower. I think this could be down to the extra material in the 333's tougher upper. Both great shoes. I used 333s over winter and have just got a pair of 272s for spring. 272s are discontinued though unfortunately, so you might find them hard to get hold of now. Try somewhere like Lakes Runner, they might be able to get hold of a pair for you. Mudclaw 300 will replace the 333 later this year, I think. It looks awesome.