And what would that difference be (apart from support perhaps)?
Need to buy a Mac for Maya
For gaming PC’s no difference, for workstations better to get them from a vendor due to the component costs and config. In other words you wont save much money on a workstation by building it yourself so may as well get one professionally built.
You could probably get a used workstation class PC for very little cash from HP, Dell, Lenovo etc to tide you over for a year. If you try to do serious work on a Mac mini you will regret it!
The only possible problem that can come from a custom PC is if you receive a part that’s not working. I’ve personally never had that happen in all the builds I’ve done, usually as long as you choose a well-reviewed part from Newegg then you can’t go wrong. That being said, there will probably be at least one person on there that got a DOA part.
Also, when building yourself, you usually get a better warranty deal. The individual parts have a much higher warranty than when you buy a whole computer, and if you get a problem with a part you can just send in that part instead of having to take in the whole computer, so if you needed to you could get a replacement part while waiting for the broken part to be taken care of. Though of course you have no coverage if you damage the parts yourself.