They're pretty similar in terms of hardware, so honestly, it's more a matter of which exclusives you want more.
As for the Xbox reliability, I've had mine for a long time now (roughly since 2008) and never had any issues with it. I've also moved with it quite a lot bringing it back and forth to friends' houses, and still had no issues.
That said, I definitely prefer PC gaming, but it's nice to be able to get a gaming machine for far less than it would to build a halfway decent gaming rig.