I have the Keyboard, and would encourage you to consider it. I don’t think of myself as a keys player - I took piano lessons for a year or two over 30 years ago and would probably dislocate a finger if I tried to play Bach or Mozart today. The aftertouch is extremely playable even if you are just hitting a random cluster of notes. The 44-key-wide touch strip is nice too.
However, if I need a traveling studio, I’d immediately buy an Explorer. I could see adding the desktop to my home studio, but I feel like the Hydra really benefits from keys.
The sound is amazing. I sent a short video of myself badly playing the Balderunner opening notes to a friend, and now he thinks I’m a synth god. It isn’t a CS-80, but it stands on its own two feet and delivers a rich sonic universe.
I’m mostly just jamming on it, it is that much fun. I have a lot of synths that don’t necessarily play nicely with others, but that’s what EQs and compressors and other mixdown FX are for.
The Virus still wins on polyphony and multitimbrality as well as FX. The Hydra has a richer synth engine that is even easier to use and it is loaded with modulation sources.
Ultimately, I think the Hydrasynths do exactly what they advertise. The UX is fantastic, the synth engine is rich and powerful. Build quality is solid and functional. It isn’t multitimbral, it has an adequate but not extensive FX section. It doesn’t take the VA concept quite as far as the OPSIX, but it is a slightly easer and more pleasant synth to work with.
Listen to demos with your own ears. When I put my hands on one at B&H the hydrasynth immediately moved from my “I’d like one someday” to “next synth purchase” list.