OK, you asked...
First off, I'm a photographer, but I play with computers to make money...so I guess some would (OK, HAVE) called me a geek...BUT...
The current project I'm working on fits right into your question since I currently have a couple of Xooms on my desk along with an iPad and a Slate (Windows 7 tablet) and had a Playbook and an iPad2 sitting here last week to work on...
Here are some quick notes:
Playbook - 7" screen, does not offer 3/4G unless you already have (or purchase) a Blackberry to use for the communications when WiFi is unavailable...I don't think the choice of applications is at the same level as Apple or Android - at least not yet...I do think I'd wait on this until they added 3G/ 4G capability as I wouldn't want to have to rely on having a Blackberry...
Slate - 7" screen, basically a netbook (not notebook) with a touch screen. If a netbook will handle your level of use, this isn't a bad choice. The good (and bad) of Windows 7 in a very easy to carry package. Note that there are also larger screen versions of Windows 7 tablets too. Most folks know what apps are available for Windows, so I'll just leave that alone...one other thing I noticed with the Slate is that it offers a USB Port and SD Card slot that aren't standard on the other devices...
Xoom - 10" Screen, Android 3.0. Note there are other sizes of Android tablets - some with older versions of the OS and some with 3.0. HD form factor screen, so a bit shorter, but longer than the iPad. Both Google and Amazon have App Stores for Android, but not all apps will necessarily work on the more recent OS (yet) and some won't be designed for the larger screen vs. the SmartPhone sized screen.
iPad / iPad2 - 10" screen - one with and one without cameras. I should have mentioned that the others all had at least one camera...You get Apple's App Store and no flash. A hard core Apple lover friend of mine described me as anti-Apple...I'm not although I do not care for their approach on some things...I bought an iPad back in January (before most of these devices were available) because it provided me the capabilities I was looking for in a better, more complete package than the other available devices. (as a side note, I have an Android phone)
My recommendation to you is to go to Best Buy or a similar store where you can get your hands on some of these devices to see what works best for you. In general, I think both the iPad and the Xoom are fairly intuitive to use, but they are different and you may find you prefer one to the other. I don't think you can go wrong with either as they both have strong and weak points.
From a photographer's stand point, all have nice screens and have sufficient space to hold a number of photographs. Since I expect I will always have a camera on my phone if I encounter a situation where I'm without my "real" cameras, I don't really care about cameras on these devices unless it was for Skype or something like that...
I know the iPad has an option to allow you to attach an SD card for downloading photos and you can also move photos to and from with a sync from PC. I doubt I will use my iPad to edit my photos, but I doubt I would need to. However, it is a great way to show off family photos, your portfolio or whatever you've most recently photographed.
Oh well...hope that helps...probably more than you wanted, but...