Ironman wetsuit questions

I have been offered a wetsuit in good condition (only one small nick) for CAD $100. It’s an Ironman fullsuit, size 4 (large). Just curious about three things - what’s the big difference between a full suit and sleeveless as far as fitting and comfort - I was hoping for a sleeveless since I thought that being a swimmer by background it would be more comfortable. Second, how do Ironman suits typically fit - tighter than most, looser, etc. I’m a border line L (6’, 220) and don’t want to get something too tight. Third, has anyone ever heard of a size 4 sizing for Ironman suits. Their website talks about S, M, L but no numbers. Granted the suit being offered is a 2001 so that may answer the question.

I have a size 2 Ironman VO2Stealth fullsuit I got in 2000 - I’m 5’9", 145lbs. I am not familiar with the S, M, L sizing - they seem to have a lot more sizes for current suits than when I bought mine. Before the Ironman, I swam in a QR long john which I recall being a much tighter fit. I’m glad I went with the fullsuit. As long as I get the suit fully on (i.e. no gap at the armpit) I get no shoulder fatigue.

I have an Ironman wetsuit: they seem to fit “bulkier” people better than some others
.

Good timing. I have been swimming in an Ironman sleeveless Instinct for two years. Let me preface this by saying that I am a shitty swimmer, though I am improving. Needless to say, it was love at first try with this wetsuit since it helped my horrible balance. I went with the sleeveless to save some money and because I didn’t want to get too hot. However, I think if I could do it over again, I would have gotten a full. More on that in my wetsuit post.

Sizing: I wear a M/L and I am 6’1", 180. The suit is snug around my neck. I thought that was just how it should fit, but after trying on some full suits today, I realize there are more comfortable options, and different suits will fit differently.

I am going to post about my full suit trial in a moment. I tried an Xterra and a Desoto two piece.