Well built receivers, as both of those are, sound more alike than different. It really does come down to features, as you were thinking.
That said, pairing an older Pioneer receiver with a newer Pioneer TV really doesn't gain you anything. That receiver uses SR+ to send the extra info to the TV. When they are connected that way, the TV must be on, and the remote for the receiver must be pointed at the TV in order for it to be controlled. While I have a Pioneer TV, receiver, and DVD player, I've only connected the DVD and receiver together with the SR+ cable. I've also used the "out" on the receiver to go into the DVD player, so the receiver is the component which must be on to control the player. For some reason Pioneer only puts SR+ outs on their TVs so they become the control point. So there's no point in using the pairing feature available to you. If you had a newer receiver you would be able to use the HDMI-CEC (aka Kuro Link), but it's pretty much equally useless.
Also the older Pioneer doesn't support HD audio bitstreaming. With it's HDMI audio support being limited to LPCM. For me, that's not an issue, as I believe that's the way it should be done (i.e. the player unpacking the compressed audio and sending the result to the receiver, rather than sending the straight bits). Some people like to see the DD or DTS lights shining on their receiver, but that's meaningless to me.
The only limit I really see from the Pioneer receiver is that it only has 2 HDMI inputs, that's pretty restricting these days, but you could get an external switch. If it were me, I'd invest in an external scaler, like the DVDO Edge, or the Lumagen Radiance XS, to get extra HDMI inputs, and high quality scaling for all my sources, and run the display in Dot-by-Dot mode all the time.
So if it's easier to live the Pioneer where it is, I don't think you'll really be losing out, sound quality wise, and only slightly in the feature area.
