When you get your Casio, don't forget PocketQuake :)
http://www.pocketmatrix.com/pocketquake/

Don't forget that your Casio will be able to play videos, MP3's, and you can do things like handwriting recognition (Newton style) with Transcriber, as well as do street maps with PocketStreets, etc.

The iPaq has numerous advantages including being smaller and slightly lighter than the Visor Prism (!). It utilizes a color screen that is reflective and can be seen easily in direct sunlight. The E125 is bigger than the Visor Prism. Neither E125 or Prism can easily be seen in direct sunlight.

But yes, if you're going just for videogames and don't mind the speed, the Casio is the way to go. But if you were hoping for something as small as your Prizm, you're in for a shock: The E125 is a brick (but built rock solid like one).