First, let me preface this short review by stating that I am a slow swimmer. Right around 30mins for 1500m (either open water in a wetsuit or in a 25m pool). Best 100m to date 1:19, if I’m doing repeats more like 1:25. I’ve been told that I have good form by my coach but that when I fatigue it gets bad quickly. 6’1"-6’2" ~165-170lbs,~ 6-7% body fat, and my legs sink like bricks. I’m not sure if there’s anything else relevant I can share here but let’s move on.
My apologies but I don’t feel like fighting TinyPic to get the orientation right. Anyways, being a competitive and somewhat well off individual I did what you’d expect me to do: throw money at the problem. Part of that was getting a coach and part of that was assembling a small stable of wetsuits (the Roka and the Blueseventy are for sale over in the classifieds 
What you’re looking at is an Xterra Vendetta, Roka Maverick Pro, and a Blueseventy helix turned inside out. Why inside out? Well, it gives you a better idea of how the suit is put together.
Xterra Vendetta: I’ve had this suit for about two months now and, for all intents and purposes, I might as well be on top of surf board. This thing is seriously buoyant. Of the three suits, this one floats me highest in the water. If you look at the picture above, you’ll notice that the suit has a large panel of thick neoprene extending from the center of the torso down through the legs below the knee. This is probably aerodome and I’m guessing it’s 5mm thick. This material makes up almost the entirety of the legs. The arms are made from a very thin material and, honestly, you stop noticing that you’re wearing a suit after a minute or two. The arms and shoulders really aren’t restricted at all in my opinion. My legs float very high in this suit to the point where if I contract my glutes just slightly the soles of my feet breach the surface of the water. I can rotate pretty well in this suit as well but not quite as well as the Roka
Roka Maverick Pro: I bought this suit a few weeks before St. Anthony’s as I had been training hard and watching my diet and was the thinnest I can remember being. As such, my Blueseventy was too big on me. The key to this suit’s construction is that panel going up the middle of the suit. I’m guessing that’s 5mm aerodome. I could be wrong. The same material is in the same place on the backside as well. The material to the side is thinner. The idea is to concentrate buoyancy along your axis of rotation. Here’s the best analogy I can give: when you’re face down, flat in the water it’s like you’re on top of a log and it’s pretty easy to rotate to one side or the other. The cool part is that once you’ve rotated about 45 degrees or so the thicker material on your back starts to be submerged so it’s like have a log on your back that stops you from over rotating. I was able to really feel this in the Roka. I could rotate from side to side hard without feeling unbalanced in the water. There was a downside (at least for me): this suit is not super buoyant. In fact, it’s the least buoyant of these three for me (in fairness it was also the smallest) and the legs don’t float in as pronounced of a fashion. I had to keep a small flutter kick going to keep my feet up near the surface. Now these “negatives” are probably positives if you’re a good swimmer: you make use of your kick, rotate hard, get the friction advantages of a wetsuit and, otherwise, it won’t get in your way.
Blueseventy Helix: I’ve had this suit for a bit over a year. It was the first high-end suit I bought. If you look at the suit, the black panels are 5mm aerodome (neoprene with air bubbles I think). Notice where they are: the seem to mirror the position of your lungs. To me, this is the opposite of the Roka: it’s tough to rotate and, when you do, you feel a bit unstable on your side. There is a plus side, however: you sit a bit higher in the water compared to the Roka and this makes it a bit easier for me to breathe in choppy water. The legs are aerodome down to about mid-thigh and then some sort of slightly thinner non-aerated neoprene after that. For what it’s worth, it feels like you can actually make use of your kick in this suit while your hips ride high. Hard to explain. Edit: Ken down below brought up the point of the Helix’s zipper which closes from the top. Some people don’t like this design and some do. I, personally, do. There’s two purposes behind this zipper. First is that, supposedly, it’s faster to unzip while running to transition. I personally don’t buy that. The second is that if someone grabs your zipper and pulls the suit won’t open up. I don’t know about the rest of you but I don’t think this is an outlandish possibility. I’ve had swim starts where people have grabbed firmly onto my legs with both hands (do you think I’m going to pull you or something?) and grab onto my shoulders to pull themselves forward. I could see a zipper getting pulled.
Short version:
Xterra Vendetta: a boat with really flexible arms
Roka Maverick Pro: really easy to rotate, for the better or aspiring swimmer
Blueseventy Helix: a pull buoy you can kick with
My dream suit: a Roka Maverick but with the center buoyancy panel being a touch wider and of a material that’s more buoyant… and a Helix-style zipper.
Worrying whether a suit is better for you if you are a leg sinker, power swimmer, etc. is, IMO, overthinking things. Get a good suit that fits you well and focus your mental energy on improving your technique. Cumulative marginal gains are what drive business for these equipment manufacturers, stop hurting the economy