I’ve always raced with a traditional tri top (compression sleeveless) and tri bottoms (compression), but it’s clear these days the new trend seems to be a one piece tri suit. Additionally, I’ve seen a lot of pros wearing a one piece with sleeves. I’ll admit I’ve been out of things the past two years recovering from a surgery, but now that I’m getting back into it I’m curious to know the reasons behind the new trend. Is it simply preference (aesthetics, style, etc.), or are the tri suits (especially with sleeves) faster, wick away better, keep you cooler, etc.? Appreciate the information.
I’m really fair skinned so I’m considering a sleeved top for the sun protection. As for full suit vs. top+shorts I’m leaning toward the two piece because it makes it easier to execute an emergency #2. This is a constant problem of mine in training but fortunately it hasn’t reared its ugly head in a race.
You need to look up and read the threads on Aero Camp. In a nutshell, ‘skin is slow’ and the sleeved suits, provided they fit right, are significantly faster than the traditional two piece kit.
One piece pros: can be used as swim skin in a non-wetsuit legal race, no waistband digging into the flesh.
Sleeves: no sunburned back and shoulders
One piece con: number 2 visit to a port-a-potty
Tri suits have been around forever.

As mentioned they are better to swim in, and (like cycling bibs) don’t have a waist band.
The downside is that they are slower for pit stops.
The new sleeved suits help with sun coverage and aerodynamics (assuming the fit w/minimal wrinkes…if not they can actually be slower).
You can get a sleeved top as part of a tri suit, or as a top-only (ex. Castelli T1 Stealth, Kwiami Kona Wings, etc.)

Nice photo of the tri suit couple. Who are they?
Nice photo of the tri suit couple. Who are they?
And I was sure that it was Frank Zappa.