YoniV so here are some things I've noticed. Mind you, this is only on my laptop which is a Lenovo S145-15API Ryzen 3 with 8gb ram.
Time from power button to logged into userspace is faster on Budgie, I didn't run the numbers to have concrete proof though
Budgie - 1.2gb ram at idle, CPU 3%ish after initial login and load (I know ram can be lower, but I like having all the applets I do that helped that number tick up)
Plasma - 850mb of ram used at idle, CPU is the same.
Normal day which includes 15-30 browser tabs, I use Opera, a spreadsheet editor (sometimes free office, sometimes libreoffice, sometimes Excel in a browser tab), a Citrix instance and applications in that
Budgie quickly ticks 60-75% of my ram, CPU load is fine it just depends on the active applications
Plasma hovers between 55-65%, again CPU usage is fine
If you want themes and options, Plasma has you covered to a point it can be overwhelming. My current set up
Global Theme - Orchis-dark
Application Style - Breeze
Plasma Style - Sweet Mars
Colors - OrchisDark
Window Decorations - Sweet-Dark
Icons - Beauty line
Cursors - Sweet-cursors
Splash Screen - I change all the time, was Orchid, then Breeze, then now Sweet
And all that is just the appearance! There's Kwin, workspaces, users, and a million other settings available.