Pure Data is visual programming language, you could essentially build native / vst / mobile apps with it and go more low level eventually. VCV rack is more Eurorack hardware simulator so to speak, musical instrument. Good for reality check before going hardware but you don't create apps with it.

PD does more stuff. The dataflow model takes some getting used to and tends to linger in the background even if you get down to the libpd level.

VCV/Eurorack is a simplified rather dated synthesis model for people who don't want to go that low. It's ideal for people who just want to noodle around plugging and unplugging things and turning knobs.

I've been sketching ideas for a next-gen synthesis language which is more powerful than PD/sc, keeps some elements of modular thinking, but adds some useful creative extensions.

If I'm really lucky I'll find the time to do something with the ideas in the new few years.

I'd love to chat. Please email me; my address is in my profile.

All the power, none of the hokey GUI.

Put simply, this is Pure Data on acid.

Ehh, I don't really think that's a good comparison. Pure Data is a visual programming environment/toolkit that gives you a set of low level building blocks from which you can build whatever you want. You can extend it by taking advantage of open source libraries that other people have made, or even code your own in C.

VCVrack is open source, but as an end user you're not dealing with the low-level stuff out in the open the same way you would in PD. It's a completed object rather than a set of legos.

Having said that, You're right about the GUI. The PD GUI is... primitive, to say the least.