I’ll be the odd one out, and say that when I had a Mangrove I just didn’t feel like it dealt with audio rate modulation all that well; the FM depth in particular seemed quite shallow.
I’d take the complex oscillator any day. I don’t have a DPO specifically, but I do have a Hertz Donut and a Double Helix; my two favorite VST synths are Aalto and Buchla Easel V, and E370 and Plaits and Rings all do FM.
I thought Mangrove had a lovely sound on its own, but also found I could almost replicate it (not quite so sweet-sounding, but close) with a squarewave VCO, Function, and a saturating VCA. In a rack already crowded with sound sources, I felt it wasn’t making a unique enough contribution.