We are simular in size ( 160 - 5' 11"+) so fitting will be simular... I've been using the Piel for about 2+ yrs. and the T1 for about 1 1/2 yrs. And, about 18 yrs. of various traditional designed wetsuits (i.e., QR, etc.). Below is my post regarding the Piel and T1 (...using a benchmark is a much better way to compare products). It defines speed in terms of removal, swimming and fit. It also seperates the difference between ease of removal and speed of removal. I did not compare the Piel or T1 to traditionally designed wetsuits since I find the advantage of the Piel or T1 to be better or equal in characteristics of traditional wetsuits.
I use both a T1 and a Piel. I no longer use my QR (long or sleeveless). The T1 is comfortable and gives a good swim like feel. In contrast, the T1 requires more effort to remove than the Piel. The Piel learning curve for removal is zero (so is the time it takes to remove it-zero seconds). You simply pull up on the zippers and run to your bike. It will fall off you before you exit the water. Because it requires no prior experience to remove, it is faster to remove. By comparison, the T1 requires test runs and experience to remove quickly. But, no amount of experience will reduce the added effort it takes to remove the T1. Bottom line, experience using the wetsuit determines speed of removal. Ease of removal is dependent mostly on fit. If the wetsuit doesn't fit, no wetsuit will be fast and easy to remove. This is where the T1 has advantages. By design, the two pieces offers more variability when fitting.
My Piel suit fits well enough and comfortable enough to wear for shorter distance tris. But it's key advantage is in it's removal. Speed of removal is more crucial for shorter distance tris than longer distance tris. As a result, I use the Piel for shorter tris. As for the T1, it dominates in the comfort category for longer tris. On the other hand, (IMHO) it is slower to remove (compared to the Piel) and requires more effort than the Piel (or most traditionally designed wetsuits). But in longer tris, transition times are not that crucial.
I like both the T1 and the Piel but for different reasons. I don't believe they make a wetsuit that is best for ALL types of triathlons.
Finally, the T1 contains less neoprene...in effect you float less (at least that is what is claimed by T1 competitors - sounds logical to me). On the other hand, DeSotto's T1 has counter that you float less where you need to float less - the torso. And, you float more where you need to float more - the legs. In effect, you maintain a more balance and level swim position. I have seen no quantifiable proof to either claim, but both arguments make sense to me. I personally haven't noticed a big difference in my swim position as a result of the T1 wetsuit.
There are a few other detail things that I dislike about the T1 (and the Piel for that matter) - but, they're not key issues (but, if you wear prescription goggles e-mail me and I will discuss one of these annoying details about the T1).
FWIW Joe Moya