I have replaced almost all piping in my house. I used PEX-B with the fittings secured by copper rings that you crimp with the appropriate tool. It is so easy to use and confirm the joint with a gauge tool.
I had to solder copper where I couldn't replace it all. Every copper joint was it's own little project. While for PEX it's quick and easy.
Either way, my lack of confidence applies to all PEX-B and PEX-A connections. They're all essentially a straight friction fit with some hose barbs. I got some PEX-AL-PEX fittings/tube too (the 1" P-A-P has 35% larger cross section than plain PEX, and PEX larger than 1" seems rare and expensive), and the threaded compression style gives more confidence.
I'm not disputing that PEX is a whole lot easier, even knowing how to do copper and just watching PEX videos. As I said, "maybe I'll fall in love". I'm just starting with piping where a leak won't be a major hassle (hydronic, and eventually compressed air), and foresee myself continuing to do copper for any modifications to potable water in the immediate future. If I had to redo the whole house, I'd get over my reservations quick!
I purposefully avoided the stainless cinch rings. This feels like the cheapest solution to me. It has some moving pieces. I found examples of leak with stainless cinch rings online when I was choosing what technology to use. Not so much with the copper rings. The copper rings are just that. A thick copper ring that you press into shape with great force. The price of the $50 crimp tool is nothing compared to the cost and hassle of a leak down the line. Add a $30 ring cutter tool too. For when you mess up (you cannot remove the ring in place, you must cut the pipe).
I have also retrofitted the house with underfloor hydronic heating. 400m of PEX in an open loop system. Not a single leak after few years.
With the copper rings the PEX takes the shape of the fitting. Even if you manage to cut the ring. The PEX won't come off. You have to cut the pipe lengthwise to get it off. I am not sure the stainless clamps perform the same.
I'm installing an outdoor wood boiler, which is an open system. But it will have a heat exchanger to my closed hydronic system for house distribution.
P-A-P seems nicer to route the pipe, but there are fewer fitting shapes. I'm considering it for a few long runs, because anything over 1" nominal seems to become rare and jump in price, and the 1" P-A-P is 35% larger than 1" PEX-B. But maybe I should just suck it up and deal with 1.25 or 1.5 inch PEX-B. (Would you happen to know a good source? I keep coming up with Supplyhouse.com, but half the fittings are out of stock and they seem expensive).
I'll see how I like the cinch rings. Maybe I'll move towards the crimp rings down the line. I figured a powered tool would be a boon for doing a bunch, and as I said it seems like for a powered crimp ring thing I'd need a Milwaukee cordless for ~$600, whereas the cinch ring I can get away with a $100 Ryobi. I can justify the latter for personal use, but not the former.
Open loop is easy to deal with. I can use the same water heater. It's the bay area in California, so the system works for 1/3 or the year. Rest of the time it's simply buffering the cold water supply to the water heater. So no water stagnating, not air vent needed, and it's always filled up by definition. Further more because it's at the street water pressure, the pump cannot cavitate, so it last longer and is quieter.
I only used manual tools to crimp the rings. Sure you need some force but your body will build muscles. And since PEX is flexible you don't use that many fittings anyways. It's really childs play.
I'm looking into adding underfloor heating myself.
