If the price is right (which it probably will be), the mini studio is good as an emergency. It definitely seems worth spending the extra for the Solid though, it's a huge difference!
The me, presently, the solid studio is THE solution for having a great tube tone without the LOUD volume of tube amps. I use it with a good tube preamp and believe me, it destroys the corresponding Helix native tone easily.
Solid studio was set to have the amp section on darker tubes, and the mic, instead of being centered where it would sound the brightest, it was set on "edge" where it's darkest. But if you take the amp section out, indeed... solid studio is more massive, a bit darker, fuller.
It's not that solid studio has more low end, it has just less highs. Due to the presence knob that shows 11 a.m. Still I have a question. As I know, the mini pedal has 24 impulses for all - electric, acoustic and bass guitars. What about its bigger version?