I have the proto ct in 154. I came off a never summer 151 (non rocker). It rides a lot bigger, in fact, too big for me. I only get a couple powder days per season, even here in colorado. It's my go anywhere / do anything board, so I don't need it for 10 powder days a year.
I'm looking to go back down to a 152 now since this board feels much bigger to me.
and yes, I used the 151 in powder just fine. I don't get many 4 ft days at wolf creek, but the occasional 1 to 2 ft that I get maybe twice a season, I just lean back
just ask yourself how many days a season do you ride full on powder. If it's more than a few, go bigger. less, and the 154 would b fine