hmmm... 2mm thicker or a half dozen dongles... choices, choices, choices...
The 2015 MacBook Pro is still an excellent machine.
It the thought of using adapters, such as Monoprice's $9 slim inline USB C to USB A adapter, or a cable with USB C on one end and USB A on the other would be too much to bear on a modern machine with incredible expansion and bandwidth possibilities, I'd go with the 2015 MacBook Pro.

