New PC.
For a main PC workhorse I still favour a big(ish) box desktop (my current is a 'mid' tower and I wouldn't go smaller than that)
Easy to work on if you want to upgrade (add RAM, SATA drives, PCIe expansion cards) without squinting and finding your fingers are too fat to get to the bit you need to without dismantling the whole thing.
The slim form factor towers can be quite limited for internal space (even if the motherboard has all the sockets for expansion). Been there done that on a couple of machines I look after for others. A PITA.
If you have no qualms about practical upgradeability then there are some decent 'mini' PC's floating around, nice small form factor, passive or actively cooled, decent specs.
https://www.google.com/search?ei=7m0LXe ... nZ_n8JL7NAThey are at a slight premium price wise to a standard box but they do look cool. (I'd happily get one as a secondary machine).
Just make sure you get what you need upfront specs wise as some of them have soldered components (like the RAM) so aren't user upgradeable (I'd stay away from those).
Likewise with many laptops these days (especially ultrabooks), lots of soldered components so either spec it for the long haul or check to see if RAM/SATA/NVMe et al is on standard non soldered sockets and how easy it is to upgrade stuff.
Ifixit (
https://www.ifixit.com/) has teardown/upgradeability scores for quite a lot of laptops, some of the more popular ones score terribly (use of hot glue, bonding) so always worth checking first.