It's swings and roundabouts at the moment. PSPware seems more stable at the moment, but iPSP has a lot more options for video conversion.
PSPware's video conversion is pretty basic at the moment, with no options for 15/30 fps, no progress bar or time-left indicator, no estimated filesize etc. If you are mainly going be to be using it for converting videos I'd definitely go with iPSP. It's being updated pretty regularly as well so I'm sure the glitches will be ironed out.
If video conversion isn't that important to you then I'd go with PSPware.