I have these pens and BOTH of them are my top two favorite pens

9

9

9 . I wouldn't give up either one of them! They're both solid, well-made pens & are superb writers. They both have beautiful styling... the Edson has gorgeous color & is perhaps flashier. The Exception is elegant in a very different way. A friend recently remarked that the Exception reminds him of a Chanel perfume bottle (!) although I'd describe it as "tuxedo." I have the model with the gold bands down 2 sides -- and if I had lots of money, I get the platinum model too! I saw it in person at the Columbus pen show and it's amazing.
I have a stub nib on the Exception (not an inlaid nib) and a left oblique italic on the Edson (a completely sexy inlaid nib), and the nibs are nails, so if you like flex or springy nibs, you wouldn't like these. I have a thing for inlaid nibs... but if you're prone to holding a pen very close to the nib, it may not be for you.
The Edson is round, and the Exception is squarish, so that might be a consideration for you. The Exception is heavier. One design feature I really like about the Exception is the bayonet mount of the barrel, so checking the converter is quick and easy.
I've had them both on flights without any leakage or anything.
So I guess I'm not much help at all

since I think they're both worth the $$... the Exception has a few different models, some of which have a simpler or more conservative appearance, which may be a plus for some people.
If you have specific questions about something, ask away -- I'm sure the Waterman fans will dive in and try to answer! Either way, you're going to end up with a terrific pen!
Petra
/:)