I live in Victoria and in the depths of winter I'll be wearing a long john wetsuit. The cold doesn't bother me that much, in fact I kind of like it - makes me feel alive. It also gives that extra incentive not to fall in. Although next winter I'll probably wear some booties.
I usally wear a RipCurl Fireskin wetsuit (4/3 sealed seam very warm) for kiteboarding or surfing in winter.
For SUP surfing this last winter in the surf I wore my mid-weight RipCurl E-Bomb (3/2 not sealed). You're not sitting in the water all day like a surfer so you're not getting particularly cold and you warm up pretty quick paddling.
For general SUP paddling I would board shorts and a rash top. I started with a rubber rash top but that got too hot and sweaty. If it's choppy and stormy and I'm likely to fall in a bit then the E-Bomb was ok.
If you're bald like me then a hat is a good thing. I almost always wear booties, mainly for better grip and to protect my feet from rocks and shells and stuff.
Four words...all of the above.... Best time of year for waves in New England is winter. It's all what you get used too. I usually pack a hot thermos of soup and a few 2 litre bottles of hot water. If you start to get to cold after a couple hours just go in, eat a little soup, pour some hot/warm water into your suit and your good to go for another hour or two.