There are three methods to make pex...the original (and still the best in features, but often the most expensive) is pex-A. Pex-b is a little less expensive and pex-c even more so. The major differences are in their flexibility and minimum bending radius where pex-A is the most flexible and strongest with the best memory. It is the only one that can be repaired if kinked without cutting the kink out and installing a fitting. It also has the least overall flow restrictions because to install a fitting, you must use the expander tool to fit it in. On -b, and -c, the fitting will slide into the end of the tubing, so it has to be smaller. Keep in mind that if you have a tub spout, you cannot use pex to run from the valve to it or you'll have issues...that must be done with copper. You can often pick up the expander tool on ebay and resell it for not much expense. It might be possible to rent one. Crimping isn't hard, but is potentially more error prone. It is easier to cut the crimp and reuse things if you mess up. With the expansion system, you generally need to cut it off, and if you're really careful to not score the fitting, you can cut the tubing off and reuse the fitting, but it may be safer to use a new one. If you mess up the tubing when cutting the crimp, you have to cut that off, too.
