Hi Andy, I have to echo some of the previous comments. In helping friends who were trying out the drysuit choices, a number of them bought and tried other options, but ended up getting a DUI shell suit in the long run. I was glad I didn't make a bunch of other purchases first (ending up spending more money in the long run). A close friend had me in the TLS 350 from day one. Incidentally, I am still on that original suit and it has been extremely reliable, over 250 dives on it, and whenever I have contacted DUI for anything they have been great on the customer service side (putting pockets on, adding turbosoles, etc). Also they are not too tough to work on; I replaced the wrist and neck seals myself.
I can say a couple of my other friends who cave dive just about 100% of their time (twice a week or more) use the Atlan neoprene suits because they like the (lower) price and the fact that they are very "slick", therefore cutting the drag factor in higher flow caves that they are in all the time (Devil's, Little River, etc.). But they also admit the Atlan suits are not as versatile as the DUI TLS units for quick drying, easy to pack, usable in all types of conditions, etc. So they get their DUIs out for colder diving and ocean stuff.
Best of luck as you shop and keep asking for a lot of opinions. Dive often - remember experience and practice pay big dividends...not to mention the fun.