What phone should by Dad buy?

I have iPhone 3G and my dad so my phone so he now wants another phone! He told me to help him, but I need help! Should my Dad buy iPhone 3G, Verizon Samsung Glyde U940 Cell Phone, Motorola / Symbol Technologies MC50 Handheld Mobile Computer, HP iPaq Data Messenger is a PDA-phone with a slide-out QWERTY keypad, or ATT Fuze, Hands On? Help me and my Dad choose!