We've used pvc, cpvc, poly, copper, and pex in our work through the years, and I just don't think you can beat standard crimp pex. It's easy to use, holds well, and I've yet to see a line freeze and burst. . . the fittings will crack, especially ball valves, but we haven't lost a line itself yet. HOWEVER, be careful that you don't let non-uv resistant pex in the sunlight for a long time, as it will deterioate and weaken it.
We use brass fittings with crimp rings, using the 100' rolls for long runs, but using the straight sticks for any short or visible runs or anything that needs to lay straight. . you just can't hardly get the curve out of the rolled stuff.
They do sell combo crimpers that do multiple sizes, but they are larger and more awkward. . . we use the one handed/tight spot crimpers, which, when in a girls hands, often become the "two handed and maybe even use the knee caps as a little help in squeezing it together" type. I do pretty well with the 1/2" crimper, but man, that 3/4". . if my carpal tunnel surgeon could see me using it, he'd be picking out his next new car in anticipation!!!!! The one handers definitely have an adjustment screw on them and will gradually need to be tightened, so if you buy a used one especially, a no-go gauge is a must. Nothing is better than going back over and recrimping every ring, ha ha. Also, if you ever have to use large fittings, such as 1", you might do a double crimp ring, side by side, as a little insurance.
The guys like the sharkbite fittings for tight spots in repairs, but in my opinion, they are awful pricey, and like John Guest and other slip on fittings, I would fear the constant jiggling down the road for the long term.
When we were planning the conversion on the 9, I bought a manifold and the little stops, and it was a pretty nice setup that I think would have been ideal for the conversion. . . sniff, sniff,
ahhh, well, coulda, woulda, shoulda
. who am I to talk. . .