in my opinion, xcel infinity is top notch for winter. others i know say the ripcurl Fbomb is much better. still, others swear by the psycho II by oneal. Its all about what fits you best. Try em all on!
depends on how cold it is....watch out for the company and their measurements though
i have a 4-3 quiksilver that feels like a 3-2 xcell... and yes they all fit different so just try em on till you find one that is the right thickness and feels good on ur body
the last thing you wanna do is be adjusting yourself every 10 seconds when your paddling out into double overhead sets