I want to see your suggestions on comparing CPanel and FASTPANEL.

I used CPanel for some time but later I changed to FASTPANEL which is absolutely free but provides you with the same opportunities. Also FASTPANEL's design looks much better than CPANEL's one. So now I can't understand why people pay for CPanel.

What panel do you guys use and why?

Plesk, just to throw another into the mix. Why? A combination of legacy and lethargy with a bit of if it ain't broke for good measure I guess...

I've used cPanel the most, but this is because it comes with every new hosting package at Namecheap. I had to install it onl;y once myself as cPanel WHM on a VPS for a project.
I don't know Fastpanel, but I see it's free for 18 months and after that you will have to pay for it. It would be handy if they would say on their website how much this will be.