Well, of the R50, MX-450, MX-810 and MX-880 I personally would go for the MX-880 if you want PC programming. Otherwise, between the MX-450 and R50, if you don't need RF there's not too much reason to get the MX-450 over the much less expensive consumer R50.

And otherwise, regarding the MX-810, I guess it depends on the price - there's nothing actually wrong with it, it's just a preference as to how I like to program things.