A slight derailment - where do you find a 7mm wetsuit preferable to a drysuit? Just curious.
When the water temps aren't quite cool enough to justify a drysuit, plus the air temps are high enough to turn a drysuit into a wetsuit in minutes from pure sweat... I find I'd rather wear a 7mm suit. For me, this generally means water temps over 60 plus air temps over 90... although there are time I'll still go dry.