I’ve ridden both. Both with 120mm forks. The FF29 was good but I found it a little harsh after more than a couple of hours. I always wanted a Solaris but they were out of stock at the time so went with the FF29. Luckily my lbs is a Kinesis and Cotic dealer so they got the frames for me. They said they sell way more Solaris frames than FF29s.
Anyway the ride. I’ve had a Soul in the past and I would describe the Solaris as a fast Soul. It’s nibble, comfy and fast. One thing I will say is I switched the Easton Haven seatpost for an EA70 and it was much more comfortable. ESI grips took away a lot of the trail buzz too, although they don’t last as long as normal rubber grips.
For me now the Solaris is my only bike. I sold my full sus because I always grabbed the Solaris. I’m now running a Raceface Narrow/Wide ring and it takes ten minutes to get the bike looking new after a muddy ride. I think this will be a bike that I keep for a long time..