Space is still a great pedal.  It has more one-to-one knobs per parameter adjustments over 12 algorithmic reverbs.  That may be quicker to adjust on-the-fly, with a faster learning curve.

“12 reverbs” is an oversimplification, because I consider that each reverb/algorithm is a multi-effect in its own right.  The older hardware still holds up well, but there’s no denying it’s a decade+ older design.

The H90 is more along the lines of 12 ‘Factor pedals:  all of the capabilities of the ModFactor, TimeFactor, PitchFactor, Space, H9 exclusive algorithms, and another set of H90-only algorithms.  Two instances of each “pedal”, in an onboard mini-mixer format.

As such, the H90 has a somewhat steeper learning curve, but with the advantages of updated hardware technology, software, and processing speed / headroom, with truly multi-multi-effect capability in a single package.

Obviously the cost differential is a big factor, as is future-proofing.  The Space is still supported, but will be end-of-line regarding any new updates.  The H90 is constantly being refined, with new algorithms added periodically.

So if reverb is your sole focus, with hands-on adjustments at a lower price point, Space will cover that.  Expanding along the lines of classic & huge reverbs, you may want to check out a few demos of the H90’s SP2016 & WormHole algorithms.