Although I don't think one suit will go year-round, for winter diving I really like a semi-dry. They usually are a 5/7mm or around that, with an integrated hood. I have a Henderson, but I've heard nothing but praise for the Pinnacle versions.
By the way, they're called semi-dry because they really limit water flow through them. So much so that I've finished dives with a dry bathing suit (which also means that you have to think about employing a "mid-dive suit warmer" as flushing them out isn't easy). And one time I didn't get it smoothed against the skin and the air pockets created some interesting bruises from the air pockets squeezing. Note I said 'one time' you learn quickly not to let that happen.
Also, that same inner surface that allows them to cling and limit all flow also makes them cling during donning and doffing. Not impossible or anything, just be patient.
I went for years with my semi-dry before finally getting a dry suit. You'll be impressed by how much better than a regular suit they really are.
Good diving.