I had a Cotic Solaris for a couple of years (29er), then went to a Chromag Samurai65 for a couple of years (27.5) and I’m now back on a Chromag Surface (29er).
For me (average height, don’t weigh much), doing the sort of riding I do (general up and down trail riding with some uplifts thrown in, not a lot of jumping or similar excitement) then for that sort of bike (mid-travel, robust trail hardtail) the 29″ wheels feel noticeably swifter, the roll-over effect is fairly noticeable but any additional wheel weight or flex is not.
🙂