My first Mac Pro was from 2008 (MacPro3,1). I loved that thing everything about it was expandable. When my work computer began to fail I was given a 2013 Mac Pro. What a difference in form factor. It went from a full blown tower to a trash can looking thing. This was very different from my old Mac Pro. The exandability was very minimal. I loved the old tower design. Everything was so easy to get to. The ram had its own boards that you could pull out to upgrade. The hard drives were mounted on rails that you could easily get to and swap out.
Apple Mac Pro 2013 - Open Case
My biggest issue with the Mac Pro 2013 was that you had to use a bunch of dongles. So you ended up with a bunch of wires coming out of it with the power button being on the same side. I also couldn't tell what the front or back was, maybe that was just me. So I ended up trying to hide the cables by making them face the back and now I had to reach the back of it to turn it on. It was also not very upgradeable, but at least the ram was.
Apple Mac Pro 2019 - Open Case
It was now time to upgrade my work setup again. This time I was given a Mac Pro 2019. Let's just say the Mac Pro is back! The tower form factor is back and with it upgradability and expandability. I'm not much of a fan of the new cheese grater front panel design but I'm happy that they returned to the tower form factor.
Apple Mac Pro 2019 - Ram Upgrade