I had a Volca modular for a while. While it’s definitely a neat offering for the price, I found it a lot more fiddly to work with than Eurorack and I just didn’t enjoy it. It’s probably more suitable for someone who enjoys working with sets of small instruments (other Volcas, OP-1, Pocket Operators etc.)
I currently have an 0-Ctrl, and love it almost without reservation. 
I used to have an 0-Coast. I really enjoyed it, and it influenced my patching techniques, module choices and my sound relatively early in my modular journey. But I found I preferred the character of other wavefolders, and LPGs that have more high-end rolloff. Eventually I sold mine, as my sound evolved and as I felt I had the functionality covered in my modular. But I do miss it on occasion, especially after getting the 0-Ctrl.