I have been trying some of the longer travel slacker head angled FS & HT 29ers recently and this year they seem a lot more accomplished. The only 29ers I struggle with still, are the cheaper short travel 80-100mm with very steep head angles that tuck the front wheel too far under the front of the bike for my liking. Like 26ers imo it will take a few more years to get enough 29ers totally dialled to suit all tastes. I have tried a couple of 650b recently that were abismal and they most certainly did not bring the trail alive.
I remember plenty of 26ers in the 90s and early 00s that cost a fortune but were dead on the trails.
One thing is for sure, 650b and 29ers are the only option in all my local dealers to demo unless it is really low end or new old stock high end 26ers at 40-60% off.
I am fortunate to be in the position where I sold my 26er before the market nose dived, then took a year off riding a decent bike so coming to it now afresh.
On the better 29ers I am yet to find a down side; instead I have found the limits of the excessively, albeit fashionably, wide bars first on tight, narrow and twisty trails.
It is still all very subjective, but I like a long travel hard tail, and until this year I haven’t found a 29er I like. The Trek Stache or Rockhopper Pro Evo both having 120mm travel are IMO, bang on for me.