I actually have gotten some really good deals on 2 wet suits.
First I bought a shorts/short sleeve one piece from Dicks Sporting goods in September - end of season clearance for $20.
It worked out very well, and kept me nice and warm for the late season riding while water temps slowly went from the 70's to the 60's.
Then during Thanksgiving week, I bought the Farmer Jon wet suit from Watercraft Superstore for 50% off. It comes with a jacket and is a full length leg/overall type suit (pluss removable long sleeve jacket). I have yet to try it out, but seems ideal for the colder spring water temps. Was too good of a deal to pass at the time.
Other than if the thing fails apart at the seams, I think any 4mm wetsuit is as good as another (or 6mm, or XXmm, etc.).