I’ve had both, if you consider the original Cotic Simple was the same as the original Soul. Ended up selling the Simple and staying with the Solaris. Mine is a medium with a Rohloff, dropper seat post and Ti brooks saddle and it still weights in at 28.44lbs inc Time pedals so I’m happy with that.
The Solaris definitely rides better in my opinion, especially on fast technical stuff. It’s very confidence inspiring in terms of….”don’t touch the brakes….don’t touch the brakes”. I had a FS 5 before and I’d say I’m arguably faster DH on the Solaris than on the 5….although there’s a bit more vision blur when you get to the bottom 😆
The only downfall of the Solaris, IMHO is that it’s a bit big and cumbersome when it comes to super slow techy stuff. I have however been reminded earlier today on here that its more than likely my skills as opposed to the bike / frame. I cannot disagree.