Never used the 'ProPex' system but did build a house 15 years ago using the Wirsbo system. Very similar to the current ProPex. Worked very well and never had a leak.Easy to use and much more reliable than crimp type joints.
You will need to use all of the tubing, fittings and retention collars from ProPex to assure tight joints. One of the main advantages to the expansion type Pex systems is that you won't need to get a crimp tool into close quarters. You slip the retention collar on the PEX, expand both and then slip over the fitting and wait for it to shrink back to it's normal dimensions.