I have had XPEL Ultimate installed on both of my Teslas (2013 and 2015) Here is the problem with PPF: though they do protect from SMALL rock chips, PPF will NOT protect damage from LARGE flying objects and dents/dings. I have had 3 large flying objects off of freeways (i.e., metal rod flying out of pickup truck, large plastic trash can, part of axle flying off of the car in front of me) hit my front bumper. Each time the object penetrated through the PPF and caused paint damage! My bumper also has small dings from the objects!
A full paint job of my front bumper by my local auto body center costed $700. PPF installed on the front bumper generally runs anywhere between $600 and $1000. So afterwards I had to have PPF RE-INSTALLED after the front bumper was repainted. So not only did the old PPF fail ($600), I have to shell out another $600 for the re-installation for something that does not completely protect!
I think the most prudent approach is to just let the rock chips of the front bumper accumulate over time and then have the bumper repainted once per year.