Volca FM: toy or tool?

I'm looking for something to make basic FM sounds, nothing particularly crazy or innovative, and I'm stuck between the Volca FM, older rackmount modules, and the Reface DX. Cost isn't an issue and software isn't an option.

The old Yamahas are too unwieldy for me, with their size and especially their weight. I considered something smaller, like a DX100, but if I'm going to buy a budget FM synth, I figure I might as well buy a modern budget FM synth. Rack modules are a possibility, but their programming and editing functions intimidate me.

I'd use the Volca FM as a sound module, with external sequencing and control (velocity is a non-issue for me). The UI, editing, patching...none of that concerns me, it can all be worked on, or worked around, but sound quality can only so far, and I don't know if the VFM goes far enough.

How does it compare to classics like the DX7? Can the experienced listener discern between the two? I'd love to hear some personal opinions.

How does the VFM compare to the Reface DX? The RDX has less operators but variable waveforms...seems preferable to more ops but I don't know enough about FM synthesis to have an informed opinion.

Finally...am I better off getting a rack module and using an editor/patch librarian? I'd prefer to get my hands dirty learning the basics of FM (if possible) and racks mounts seem too limited in interface for that, even more limited than the VFM. I could be completely wrong. The Volca seems limited as well, but at least it's new and therefore has a lot of support.

Basically, I am looking for a hardware FM synthesizer that can provide quality sound. The VFM is cheap, has the DX7 engine (more or less), and is small. The Reface DX has variable waveforms, an apparently easier interface, and a keyboard. Rack modules are small, can have powerful/classic FM engines, and have a big 'cool' factor (IMO). Am I missing anything?

I'd love to hear peoples' thoughts on the matter!