In PhotoKast, any photo can be used -- old scanned snapshots to camera shots, to phone shots. In PhotoSwap (unless anyone has hacked the software yet), only a picture out of your phone will work.
So on PhotoKast, you see a lot more posed pics, professional shots and old modeling pictures. No full genitalia nudity is allowed on a kasted picture. Here are some PhotoKast pics:
The pictures tend to be a little more crisp and sometimes staged than on PhotoSwap. Leaving a message to a particular photo taker can be fun on PhotoKast, but I find most of the return pictures are guys clearing out their photo albums of ex-girlfriend pics. Some are quite good, but it's like using a blow-up doll instead of a real woman. You can also leave text messages to picture senders. I prefer fiddling with PhotoKast when I'm in line at the post office or somewhere and let old ladies behind me see what's coming up on my phone--that's just me though.
On PhotoSwap, the pictures tend to be more raw and lower quality in nature--but they are also in real time (of course, except for the fake "pictures of a picture" swapper). Notice the difference in the PhotoSwap pics:
The lighting isn't quite as crisp in the PhotoSwap pics, you can see blemishes, the focus is sometimes not quite right. But the pictures you can get off-the-fly are a lot more surprising. Sure, most are shitty pics of keyboards and hairy legs, but once in a while a gem pops up on your phone.
On PhotoKast though, there are some funny pics people decide to kast out:
Which is better, PhotoSwap or PhotoKast? Well, if you like the grungy garage-band type pictures that are more spontaneous, PhotoSwap fills the bill a bit better. If you like the tailored sound of a good studio album, PhotoKast pics are better. Leaving messages and potentially swapping on PhotoKast makes it a bit more interactive within the app. Though on PhotoSwap, I find hooking up via email or by other means after initial swaps has turned out to yield more pleasure for me. But the call is up to you...