As a part of troubleshooting my lost heartbeats issue, I swapped the locations of my R600 and R710 to rule out the underlying wired network. But at any rate, this leaves my R710 in my office and my R600 in the geometric center of my place.
I did a test for fun, connecting to the R710 from a 1-stream AC smartphone on 5GHz from the opposite edge of my place, through 4 walls and a washer/dryer stack. To my surprise, I can still get 100mbit of download and ~50mbit of upload, when before with the R600 it would barely be able to hold a connection, and simply setting the phone down on a table would cause it to lose almost all upload connectivity.
If I were building a network from scratch today (and cost wasn't a factor), after this test I would choose R710's hands-down. Even though it would seem on paper that the R710 wouldn't benefit non-wave2 clients, it seems like in practice it delivers superior performance to even legacy clients!