Using both AC68P & AC86U ... which best for Router?

I 've been using two AC68P in my house to get coverage. I just acquired a AC86U to replace one as I hear it has better speeds and also Smart Connect. Should I replace the AP (top floor, 3 level home) or the Router (bottom floor, basement) to get the best use of the 86U?
I've only ran the native QOS, DHCP reservations ,etc ... no fancy 3rd party apps or parental stuff on the router but if the 86U can handle it maybe would consider some. Suggestions are appreciated!

running Merlin on both.

thx!