Comparing a 29+ to 26, the 29+ can't corner as sharp but it rolls over everything. In some ways the 29+ feels more efficient than the 26. With bigger tires, I have way more clearance for bikepacking bags. I'm not sure if there's much difference in clearance between 27.5 and 29, but space for bags might be something to consider.
From talking to others, your height might come into consideration. Some shorter people I have talked with said 27.5 bikes fit them better than 29.