Touch is probably the best / most accomplished one overall. The Buchla pushed to its limits. It's all analog but the details are so sharp it foreshadows digital.
Basically if the back cover says Buchla, then buy it: Subotnick mastered that machine. I hear many of the organizational & editing principles of 50's edited musique concrete & electronic music on those records, he'd absorbed that aesthetic and when he was presented with a real-time synth with that abstracted metal plate controller, he knew what to do with it, the Subotnick records sound like they grew out of wild live improvisations. They're obviously sequenced & edited as well, but you can hear him flailing around on that touch surface when you listen, rockin' out...
The big six: Silver Apples, Wild Bull, Touch, Sidewinder (snakey drone record!), 4 Butterflies, Until Spring. Sky of Cloudless Sulfur also has some amazing sounds.
In the 80's he began integrating live instruments & vocals, and I'm not as keen on those pieces. I saw him and Joan LaBarbara play Jacob's Room in the late 80's in Berkeley, fairly pretentious new vocal theatrics. "Return" is a DX7 / sequencer record and it's okay but not great. There are pre-Buchla, early 60's pieces on compilations I have that I should listen to again.