Memory.
Then as now it’s memory that matters.
Anyhow if you want a brand new Commodore 64 get it here:
An alternative that's a bit like cheating since it's not a real C64 but a lookalike running VICE is getting a TheC64.
https://retrogames.biz/products/thec64/
It looks a lot like a C64 breadbin, with an actual working keyboard, but inside there's an ARM and of course it outputs to HDMI and has USB ports for pendrives.
It's a good middle ground between "just an emulator on your laptop" and "a real C64 with all the inconveniences".
For me a good portion of the appeal of a nostalgic device like that is the display. Any recommendations?