I went back to a hardtail for racing for a year, I found it was fine on the descents, you just tend to bounce off things, but it was slower climbing and on the flat. With FS you can just sit and turn the pedals over, with a hardtail the back end’s skipping about all the time.
That’ll depend on your pedalling style though, I never tend to pedal out of the saddle, people who do will probably get more out of a hardtail.
Swings and roundabouts and that…