Actualy, just avoid early models the ones without hdmi ports and memory cards. But they're beautiful. They tend to present the infamous error ring of death.
Anything beyond (including) falcon should be good...ish. But if you choose for phat, prefer jasper.
The newer models are cooler, spend less energy (model e). I don't like them for not having component cables support for using with crt tv. They also has lesser usb ports (i have some wired controllers, and external hd).
I personaly like (and have one) RGH slim on trinity mobos. Boot times are perfectly fine to me like said, 6~20 seconds. If it breaks, any technician will know how to fix.
kinect are plug and play on slim and E models, but not on phat models.
Every couple years change thermal paste, clean the fans and you should be fine, on any model you choose.
