Hey man. I have a 6/5/4, surfing on vancouver island, canada. Most people around here just use the 5/4/3 (sometimes the drylocks for extra warmth) but I like to have good long sessions (often 6-7 hrs with only about 25 min. break somewhere in between ) so I went for the warmer suit. They are definitely heavier by a bit. At first they feel a bit more restrictive, but I found after a few sessions of feeling the heavy arm-pull (when the material under your armpits drags on your arms as you paddle) it stretched out and conformed to my dimensions. Now I don't notice any more restriction than a 5/4. So for me, cold water + long sessions = I want a warmer suit. 6/5/4? No Problem.
Good luck! ..happy cold water surfing!
