I've recently updated waifu2x and I've seen it now supports lots of algorithms for different use cases and contexts and it also supports other tasks like frame interpolation. So could you briefly explain in what is cupscale better than it?

Cupscale supports multiple models tuned for different types of content (including Anime like waifu2x): https://upscale.wiki/wiki/Model_Database

As I said Waifu2x too supports many different models aimed at different content, so what's the big improvement with Cupscale?

Well in that case I might be wrong.

Considering waifu2x is the name of an algorithm I assumed it was just that algorithm. There's also no mention of other models on the demo page or the Github page as far as I can see.

My bad! Yes Waifu2x is just a single algorithm, you are right.

The confusion originates from the fact that I was using a GUI project for Waifu2x called "Waifu2x Extension GUI" (https://github.com/AaronFeng753/Waifu2x-Extension-GUI) which other than Waifu2x also supports other algorithms like Real-ESRGAN, Real-CUGAN, SRMD, RealSR, Anime4K, RIFE, IFRNet, CAIN, DAIN, and ACNet.

So as you said Cupscale is surely more advanced than Waifu2x (the single algorithm), but do you think it's also better than Waifu2x Extension GUI?

Thanks, that’s actually the “better” model that I referenced. You can buy it with an in-app purchase using the waifu2x app.

Buy what?

I think he refers to the premium version of Waifu2x.