Wesabe is too free form and doesn't provide enough reporting or structure, while Mint is the exact opposite. It provides too much structure, though the analytics and reporting tools seem like they would be great, if they could handle a more flexible set of categories.
Here are the categories for Mint:
Why are books under shopping, and why isn't there a place for me to keep track of my business expenses?
Point being, it doesn't have to be one or the other. You don't have to choose between having a completely unstructured list of user defined tags or a fixed list of categories. Do the work for your users. Come up with a flexible list of categories that you initially suggest, but the user can move away from as soon as they get the hang of things. Build reporting tools smart enough to support this, so that you can continue to tell that user useful things about their spending habits, even as their categories change.
Mint is definitely closer to what I want, but Wesabe's tagging is more flexible. Maybe the next stop will be with the big boys, Quicken?
Update: Here's another review of Mint, and another from Webware here. I'm really getting sold on Mint. It definitely is the best choice if you don't have to track things like businesses expenses, and you need to get off to a nice, easy, informative start on personal budgeting.
The Quicken vs. Mint review has already been started here, though it probably needs to be updated.