i think if you buy a high end 3/2 you will be find with hood on the most extreme days.you will only want to stay out longer then 90 mins if it's going off.If this is the case you will care more about the waves then the water temp.I surfed all winter in a 3/2 last year and kept the 4/3 in the closet like mikey jackson.
i have never had a 4/3 and i survive in OC md. if you get a really good 3/2 and all the other gear it will be good. its nice cause you can use it all year round. and it saves money. i have a hurley with the fireskin inside. works beautiful
I think you could make it with a 3/2 with the accessories..boots, gloves, hood. You might try layering a vest underneath (~$50) before investing up to a 4/3. It really is about your own tolerance and whether your endurance is greater than you can last the cold. If you have to have one or the other go with the 3/2 and good thick boots, hood, gloves. You don't want to have to get into a 4/3 until you have to. Last year I think it got down to 48 or so degrees and I was thankful for the 4/3, but before you knew it the water temp was creeping back up.
I was out in Delaware where the water was in the upper 40s maybe 50 with a 3/2 and no gloves or boots, cause i couldn't find them, and was able to stay out for a little over half an hour cause it got dark. It all depends on your pain tolerance, some people think the 60s is freezing and need boots where I think i could go out in a good 1 mm long sleeve top if it was a nice day out.