Last two years been back and forth.
Main observation is a similar-width 700c rolls a bit faster, and has a better 'attack' angle across rough stuff to take down the hits a little.
This is using 1200gm wheelsets for both sizes, and a preference for lighter+fast-rolling tyres.

Saying that, if just cruising/exploring around at a slower pace, the wider [frameset max 2.4] 27.5 is a lot of fun, with its float and cushion.

At the moment am seriously considering a custom frame that will allow 29x2.2 [designed around 44mm-2.2], but still have the same trail figure and bb height as the current ride with 27.5x2.2.
Chainstay a little shorter also [kinked seat tube]. This will have more toe overlap, but am fine with that.
Basically looking around a 430cs. 285bb. 72hta. Same reach and stack.