Personally, I'd go with Daikin if I was buying an average efficiency(17+/-) mini split today. If I wanted a super high efficiency model{30+/-), then I'd go with Mitsubishi or Fujitsu.
Daikin invented and developed the variable refrigerant volume concept back in the early 80's. That's the inverter based system used today by all mini split manufacturers. Daikin, in cooperation with Carrier, developed R-410A refrigerant as the replacement for R-22. IOW, they're much more than an office and warehouse pasting their name on units assembled by some unknown low bidder.
Although Daikin is fairly new to the US market, they've been around for a long time and have recently moved ahead of Carrier as the world's largest manufacturer of hvac equipment. Most everyone else selling average efficiency minis is simply buying Chinese assembled units rebranded with whatever name. Based on the price, Daikin is likely also manufacturing their minis in China or some other low cost location, but there's a big difference in an actual manufacturer producing goods in China versus resellers who do no manufacturing and simply buy from a Chinese assembler.
Re the warranty, Daikin requires that the unit be installed by a hvac tech. They do not specify installation by a licensed hvac contractor. The OP says he has friends who are retired from the hvac trade who are willing to help. Assuming one of these guys worked as a service tech, he would have the EPA license for handling refrigerants and that should satisfy the tech requirement. The manufacturer is concerned with proper testing, evacuation, and checkout at startup as it relates to warranty. Daikin has a 10 yr parts warranty.
Lots of people seem to be all ga-ga over the Mr Cool DIY and their lack of any involvement by a tech to validate the warranty. But, if you read their warranty terms, any warranty parts return must be handled thru a Mr Cool servicing dealer. Looking at the dealer locator on their website, the closest dealer for me would be 125 miles away and I live in a town of 90,000+ with a county population of 260,000. IOW, they don't have an extensive dealer network for handling warranty claims should anything arise.
The concept of quick connect precharged line sets is nothing new. Both Trane and Carrier used the same sort of thing with connectors made by Aeroquip on residential split systems for a while back in the 70's. Both quit using them after a few years due to leak problems over the long term. I can't say the Mr Cool units would have the same problems over time, but Aeroquip has a top shelf reputation worldwide for making fittings that work and it didn't work out real well for them.
Mr Cool is charging a premium price for units purchased from a Chinese assembler, upward of 40% more for a DIY one ton as compared to other similar units from what I can find online, so that "no tech required" warranty definitely carries a fat premium.
