for spring reverb I like the one in the Roland 103 mixer the best. it sounds smooth and clean without sacrificing character and is better at keeping the high frequencies. supposedly it’s the same spring tank as used in the 201 space echo, which I’ve never tried, but the surrounding circuitry may make it sound different. right now (if i need a spring) the 103 is working well for me, although it’s quite limited as a mixer…
the best sounding one (digital/HW unit) I tried was Lexicon 300. mine died years ago and is unfixable, and I’m too depressed about it to get another one, I think it will just die again or something. I tried a 480 at someone else’s studio and didn’t think it sounded any better.
mostly though I use the Valhalla plugins… I have the whole set. I use Plate and Vintage Verb most often. I’ve found Ubermod in 16/32 tap mode also great for reverb, in terms of very smooth reverse or infinite reverbs, and unlike the others it’s extremely flexible for novel/crazy effects. something about it reminds me a lot of a Roland unit (RV-800) I sold. The Roland had excellent sound quality, I just grew too frustrated with the remote/UI, it’s like you’d make a change and wait five seconds for the thing to respond.