I own both a Mopho SE as well as a Pro-2 presently, and have owned a Pro-One, a Prophet-600 and an Evolver Desktop in the past–but do take what I have to say with a grain of salt / your-mileage-may-vary, etc.
If you want a Pro-One, get a Pro-One (VCO, Curtis filter), and put up with the maintenance / quirks / etc. that are part of the experience. You need to ask yourself as to which elements of the experience are must-haves, versus take-it-or-leave-it (e.g., fixing the contacts on the J-wire keyboard variants); in some cases, you may just give up on the concept (as I did) and look for something else.
If, on the other hand, you're looking for something that's quintessentially a Dave Smith design, but can do most of what the Pro-One does, you've got at least four different monosynth voice options in the Evolver (hybrid DCO / digital, Curtis filter), Mopho (DCO, Curtis filter), Pro-2 (digital, SSM + SEM filters), and the Pioneer Toraiz AS-1 (VCO, SSM filter). Each does certain things well, and nearly all are more capable than the Pro-One as an instrument.