What a drag.

Try putting a dry shirt onto a wet body and see if you'd save time doing that rather than wearing it for the swim like it's supposed to be worn

I'm not a dude, but I had a tri top and shorts and HATED the feeling of drag on them. Lots of people like 'em, though, so maybe I just had the wrong brand or size. Now I have a trisuit with no pockets. I'd go shirtless if I could and get a full zip bike jersey to throw on in T1. Pulling a tight shirt over your head onto wet skin is a hassle, but sliding into a full zip jersey and zipping it up wouldn't be too bad. At any rate, you can do a few test runs and see what works.

I saw a T1 instruction video of what NOT to do (YouTube).  They showed this guy struggling to put on a shirt. It Probably took him 30 seconds. Would I be 30 seconds or more faster in the water without it? (.5 mile swim took me 18:39 with it on) I would try to time myself but I'm afraid there are to many other variables.

I doubt it drags you down by 30 seconds. For me, it's more of a mental thing. I can feel the drag and it messes with my head and makes me feel slow.

Had the same question for my OWS last weekend.  It was going to be a warm day. 

Tri top on benefits - kept me cooler on the bike, didn't have to mess with it in T1, Sunburn protection, a little more protection if you crash, show off your great Tri body (which I don't have).

Top off - No feeling of drag (I felt it for the first 100 meters than it was fine).  Help eliminate your farmers tan.  Cooler on the run.  Can hide your not so great Tri body.

Good luck.  I wore mine and still not convinced I made the right decision.

Actually, there have been studies that show you are cooler with a shirt on. But that's for running, so we'll leave that out.

Mine has no pockets and fits snugly all the way around. Perhaps because I'm female and come with some non-aero body designs, but I actually felt like the tri top REDUCED my drag in the water due to holding me in nice and snugly.

One less thing to bring to T1, one less thing to remember to do, one less thing to take time to do, one less thing to worry about, one less thing to go wrong. Hmm, yeah, I'd definitely have the top on in the water. Do not underestimate the amount of disorientation coming off an OWS!!

In a race last year, I swam and rode the bike without a shirt but picked it up in T2 and put it on while running. It was a sprint, so sunburn was not an issue.