Well, the Samsung is the most expensive and has the most features. The Motorola only has 5.5MB memory, the Sony Ericsson has 50MB or so, don't know about the Samsung.
I think I am going with the Samsung, but I don't know if I can get it because it is only for existing customers, but I know the URL to the form to order so maybe I could get it.
If I can't I will probably get the Ericsson because it has better specs than the Motorola and I heard the Motorola has many firmware problems.
Also, the Samsung has a 1.3MP camera, the Motorola is probably the 0.3MP version just like the Sony.