The Centro is slender, has a keyboard, and palm os performs as a phone much better than windows does IMHO. Easy and intuitive to use. Windows on a phone always felt bulky, clumsy, and non-intuitive to me, even if it does have more raw power.
Plus there are thousands of great palm apps that can be had for free, tons of great free jewish apps, and using it as a modem is a breeze.
The build quality of the 2nd generation Centro is top-notch. I do agree to avoid the 1st generation though. If you get a Green Centro then you know it is a 2nd generation device.
Am I biased? Perhaps. I've been using Palm OS phones for a decade now and the Centro for over 4 years now! Of course that'll end the day the Nexus Prime is released if not sooner...