I've ridden 26" bikes for 20 years and have been riding 29ers for about 5 years.
Just rode my first 27.5 bike the other day...Cannondale Trigger carbon...and as much as I like the bike/suspension, I felt that the 650b wheels were a waste. They don't roll like 29s and they don't turn like 26s. That's my opinion based on one ride on one bike.
Yet I digress...
Ride them both and see which one you like better; which one fits, which one steers, which one you feel better balanced on and then buy the one that wins. If you can't decide, buy something else.
There are an awful lot of bikes being made these days and you have many more than 2 to choose from if you're willing to wait.