Because I feel better on 27.5 than in 29ers, I don´t like big wheels in narrow and twisty paths (I don´t want a gravel, but a light XC is fast in gravel paths with some nice tires) . And because is the gap in my garage. Double Susp? No, carbon fibre ... no, aluminium no (I have the Comencal Meta HT, aluminium and weights arround 2.5kg the frame only). I have or I had that stuff. The only thing I didn´t/ don´t have is Titanium frame and steel modern frame.Any reason you’re set on 27.5?
If fast xc is what you want then 29er is a no brainier. Faster rolling and with geometry now sorted they handle just as well as smaller wheels.