I started my DSI journey with an OB6.
I did have a prophet 600 with gligli mods but I never really clicked with it.
In 2017 I tried an OB6 and I finally found the sound that I was looking for in 25 years of playing and owning synths.
I then added a REV2 for more atmospheric sounds and emulation of other vintage synths (CS-80, VP-300, polymoog etc) but I still needed a mono and the PRO3 was released.
If I had to get rid of one OT would be extremely reluctant but it would be the REV2. I can do everything I need with an OB6 and a PRO3.
There’s nothing like the OB6. It has Arps, sequences, pads, leads, complex textures, effects, easily accessible presets. But most importantly TONE. There is nothing like the OB6, not even the PRO3.