Sleeved one piece is considered to be the fastest type of suit. That's my default suit unless the weather is going to be warm or hot, in which case I wear a sleeveless one piece.

Why are you comparing a sleeved two piece to a sleeveless one piece? Personally, I find a one piece to be more comfortable because there's no waistband. Same reason I prefer bib shorts for my road bike over regular bike shorts.

I am comparing them because I can get a sleeved two piece for a whole lot let (sale) than the sleeved one piece and the same price as a sleeveless one piece.

I don't have any experience with a full piece suit. However I do 90% of bike work outs on my trainer with just tri/bike shorts and will do runs with a tri top and shorts as well. So I figure if I do that already with two piece suit why not do the sleeved piece. But if the aero advantage is lost on the two piece because its not as tight to skin and has more wrinkles then I would gladly grab the sleeveless one piece.

1st world problems and like I said I am probably splitting hairs in time gain/loss in regard to aero and probably more a debate/preference of comfort.

I've raced in a lot of kits over the past 13 years - two piece sleeveless, two piece sleeved, one piece sleeveless and one piece sleeved - and have kept track of my power, times and usually add some notes about the weather to my race files and I haven't noticed any difference in times based on my kit. In fact, some of my best times were in two-piece sleeveless kits that didn't even fit that well and were baggy in the chest when in the areobars.

The biggest thing is to make sure it fits well and doesn't get really baggy and catch wind on the bike, especially when wet. I tend to prefer one-piece for short course and two piece for long course. I like sleeves for long course for the sun protection. I guess I prefer sleeveless one-piece for short course because I'd rather run without sleeves, especially if they're tight, but it doesn't really bother me much so I could go either way.

I agree, I think that fit is the biggest thing. That if you have wrinkles and fabric hanging all over the place it doesn’t matter what you are wearing it’s going to be slow and more than likely uncomfortable because you will run raw all over as well.

I know the sleeves vs sleeveless debate has gone on for so long I didn’t know if there was a group that had looked at the difference of the one piece vs two piece.

With doing so many different length races this year, what’s the harm in having two suits?

I'm in the one piece camp. I mainly use a sleeved 1 piece these days, but the only time I would consider a two piece is for long distance race, if a front zip 1 piece isn't an option (getting out of a rear-zip one piece in a port-a-potty can feel Houdini-esque mid-way through the run...).

Otherwise, you tend to get less bunching with a two piece, and they tend to chaffe less...

Having raced with many different trisuits styles, I came to the conclusion that it all comes down to managing the chaffing. For me, I race with sleeves but gotta bodyglide the armpits a ton.

A one piece front zip is the other option. I agree with the rear zip. I tried one once and was like nope, my joints don't allow my body to move like that in a port-a-potty.

My main thought is for the Ironman. Is a sleeved two piece going to more aero than then the one piece sleeveless? Is the time difference really going to be enough to make it a worth while point to worry about. If not then the decision for me is the sleeveless one piece. But if the sleeved suit will cut off some time i.e. a couple of minutes, then its worth it to me.