Get the full size "tower" the little ones are nothing more than a laptop crunched down, and very hard to work on, such as adding RAM or changing out the hard drive.
I think DELL uses the term mini tower for their full size computer.
But myself, I would shop ebay for a lightly used DELL optiplex 9020 with an I7. https://www.ebay.com/itm/Dell-Optiplex-9020-Intel-Core-i7-4770-3-40G...
Just contact the seller to verify that it has Windows 10 authenticated and ready to go.