As always, iFixit has documented teardowns of the new Mac mini and MacBook Air, and given them a repair point. The Mac mini is an improvement over the 2014 model in some ways. MacBook Air has some positive points for ease of use, but it requires a significant teardown to do a lot.
With the Mac mini, iFixit started to open the cabinet just after turning off the fan to get in. The logic board can be removed without special tools. Unlike RAM for the 2014 Mac mini, RAM in this model can be replaced. It is covered in a metal cage, but when you unscrew and remove it, it is easy. The power supply can also be removed and replaced, but you will use a tool for it. On the negative side, the CPU can not be replaced, and damage to any ports will require a replacement of logic card.
Moved to MacBook Air, iFixit found it easier to access than any previous Mac laptops. When in, the logic board can be removed just by unscrewing a few screws and pulling out any cables. Unfortunately, do this to replace the battery. Furthermore, the RAM is not interchangeable, and the keyboard is built into the case, so it's important to work to operate it.
iFixit gave Mac mini a six out of 10 for repairability and MacBook Air a three out of 10. For more information, visit teardown pages for each product.
Listing image by iFixit