I can only compare 26er to 29er as I recently (finally!) upgraded from an old hardtail with 26er to a new full suss (140/130) trail bike with 29er. I will also get a new hardtail with 29er.
I am pretty tall (190cm) so the large wheels feel good to me. I have only very limited experience with 27.5er when I borrowed such a bike.
Of course, as already pointed out, there is much more than just wheel size and my new full suss has many advantages over the older hardtail with 26er besides the wheels.
The 26er were very agile and great for tight u-turns on narrow fire roads and trails. My 29er climbs really well but as already said, I have limited experience.

If possible try out different bikes, ideally with a very similar overall setup so you can compare the differences between the wheels without adding too many additional variables like very different geometry, suspension, etc.