Its always better to be on the most current hardware. As they make improvements to their service older equipment will not support allot of things and will not be able to take advantage of newer features. So yes its better to have the newer models which can effect your PQ plus will not limit your abilities. So just like with any hardware at some point you always have to upgrade it's always been that way.
I have to disagree about the Newer Equipment is always better.
I am greatful that I stuck with my HR20-700's and did NOT upgrade when the new stuff came out (HR21,22 and 23).
My HR20-700's were far better than any of the ones I just mentioned.
I have since went to the HR24's for 2 of the 4, the only problem is I have to go out and buy my own AM21 for the two HR24's in order for them to be able to get OTA channels. (I like to have my OTA working when the bad weather comes around.)
D* would not send me any AM21's .... they could not access them in the database.
I Ordered from Solid Signal, got my 2 AM21's, cost me $ 125 for them all because D* decided to remove the OTA tuners awhile back.
They also would not ship them to me, so in the long run I paid more for my AM21's than if I would have got them thru D*, all because D* would not send them to me.