Well, in the end I stayed with my iPad. But I didn't use it to delete lots of photos, only to store them and make a selection of the best photos. Quickly deleting those non-selected photos was not possible. I did use it however for many other things: as backup for my photos, to keep a travel journal, reading books (including travel guides), browsing the internet, etc etc. I really liked to be able to do all that with such a small and lightweight device.
A week ago, though, I lost my iPad. I'm afraid I accidentally left it on the train when I went to the office...
So I was looking around, trying to decide what to do. The thing is, I have gotten a few apps and ibooks over the last months, so I have more or less already "invested" in the iPad platform (not too dissimilar to a camera mount I guess). But then I found out that there is a new version of Photosmith that apparently lets you delete images on the iPad. It does this by importing all the images into its own sandbox instead of using the standard iOS functionality. A downside could be that other apps cannot access the photos anymore. But if Photosmith does everything I think it does, I don't think I'd mind that too much.