Anecdotally only, I know multiple people who have done the Mr. Cool DIY kits who have had issues ranging from minor to catastrophic. Some may have been installer error. Some were defective parts out of the box. Regardless, the parts are generally way more proprietary and often only available from the manufacturer.

I decided to go with the more commercial systems and just DIY'd 2 Daikin setups, one 3 ton/4 zone and one 5 ton/5 zone.

You will absolutely need certain somewhat specialized tools. I went as far as to get my EPA license to be able to purchase 410a from reliable channels. Overall the cost was still way less than what HVAC contractors are getting these days.

This is only anecdotal I know, but I am very happy with how the diakin systems have performed.

I went with a Daikin and it's much quieter than a friend's Mr Cool.

I had to make this choice recently and went just with a regular split VS diy.

There isn't that much difference, but you have much more choice in the non diy.

The only specialized tools I had to buy was vacuum pump and flare tool, for cutting copper lines.

If you take your time and are good diyer it's really not that hard.

I went with a big named HVAC supplier in the area and got a Mitsubishi. It's a work horse but I don't have all the cool tech features the newer Mr Cool units do.

They also charged a ton, even after I negotiating a much lower cost. I should have just dropped the deal all together but they did do a good job.

I have a two-zone split system in my home, and I put one out in my detached garage, which became my office after a second kid. I hired a company to put the one in my house, since it was my main house and if I fucked it up I'd be paying for it. The one in the garage I did myself, with help from my uncle who is just a fountain of knowledge, which came in handy. Getting the evaporator up on the wall, no problem, I ran the electrical, put it into the panel in the garage, no problem. Only place where I ran into an issue in my knowledge was charging the lines, but I don't think it's totally beyond learning.

Anyway, Carrier in my house, and Pioneer out in the garage. As far as how they function, the comparison is a bit apples to oranges, but the garage is fantastic. I went with 19 SEER v. 21 in the house, and I think it's great for the garage, I sacrifice a little efficiency for it to be able to cool/heat rapidly. I use it in the winter and summer, and I'm in Zone 6A for reference. This will be third summer for them, the Carrier system (May 2021), and the Pioneer was August (although I might not have installed until Octoberish, because I take my time doing things.

Yeah, just anecdotal. I think the main difference I've read is warranty support. You will not get comprehensive warranties unless you go big name with professional installer. It reeks of bullshit, but I guess I get it, it's not something simple.