I understand that there are many reasons to buy a V3 hub instead of a V2; the primary ones being WiFi if you do not have a convenient ethernet connection and thread radio(s).
However, Is there a reason to buy V3 and not V2 - #2 by MinerJason points out that the V2 hub has double the memory of the V3 and double the cpu speed.
The battery backup of the V2 is a bit of a moot point; if you don’t have power, what are you controlling?
For now I am happy with my cheap V2 (I even bought a spare). If support is dropped, I will move.