Being able to watch OTA on TV2 is a real benefit.
I guess if my 622 dies, I would opt for a 722k.
That was one of the reasons for me. Actually one of a couple, which were:
-OTA Ability On TV2s (I have a few TV2s!)
-Compatibility With DISH Sling Adapter
-Larger HD (although I also have an external HD, anyway, now)
-You can also record something like 2 OTA and 2 SAT channels at the same time time (not a hug deal for me, but nice to know I can.)