LGCU500 or HTC 3125
The 3125 is like a hybrid between a mobile phone and a PDA. The 3125 runs on windows mobile 5.0. You can access and edit more file types on the 3125, like outlook, and many other Microsoft products.
In my opinion the 3125 is kinda slow. Its nice looking though. It has a sick cam on it also.
The LG is more user friendly than the 3125...It runs on our new 3g network, (in some places) it has cingular video software, nice crisp loud ringtones, and an easy to use media player. (the 3125 is kinda low, ringtone wise)
Both phones are really nice, but after playing around with both, I would go with the LG.
I hope this helps you. Let me know if you have any additional questions