Hiya BrianE,
Definitely WAM as it's the more secure setup. The only thing you cannot control with WAM is your customers' mouths so they could share the info with someone who could then access it also as there is no actual personal login created. The login that is actually used is just to access the site, it doesn't do an actual login inside the site at all. This just means that the customer could share it. One way I would suggest combatting that issue would be to make your customers provide their main emails and use that as their login info. People are less apt to share information if it contains anything personal of their own so it helps a bit to be as specific as possible on their accounts.
Other than that, WAM is a perfect solution to what you are talking about. Give the trial version a whirl and see how it works and that should help. Create a test site so it doesn't add things to your wholesale shop and take it from there.
Enjoy and good luck with it, I'm sure you'll love it like many of us do for all it's versatility.
