I've got xpel and works great, especially if you go skiing a lot like I do (I can hear stones blasting on the windshield). I think either xpel or stonegard works fine, if you find the RIGHT installer to do the job. I had a local installer do it for me for MDX but did one myself after watching this guy on my other car. If you can find a local installer, he or she may be able to get one from xpel or stonegard at a CHEAPER PRICE then for you to order one directly from xpel or stonegard. I paid ~650 for full xpel kit (including light guard) with installation. I would have paid $700 for the full kit if I bought direct from xpel (without install). If you're handy, find a local installer, buy a kit through installer, and install it yourself. I bought a xpel kit for another car from the installer for about $200 cheaper than through xpel and installed it myself. But as a warning, installation on MDX isn't so easy. If you do it yourself, keep the film wet with alcohol at all times. Films stays pliable and you won't leave finger prints on the film if you keep it wet. Plus you get more bubbles if film dries out. Helps if you see someone install it in person.
One disadvantage of clear bra, I've heard, is that over time, wax can build up along the edges of film, which can leave a mark. After waxing, make sure to remove all wax at the edges (I use my finger nail wrapped over thin cloth). Hope this helps.
Warranty wise - here's what I got on MDX.
5 yr warranty on 3M paint/headlight protection from my installer (but I think this holds true for all installation by xpel qualified installer - do a search on xpel site for xpel qualified installers). Installer told me they last at least 7 yrs. - pretty much the lifetime of your car. You can also remove them if you don't want them later, but I don't see why you would want to remove them.
Warrenty on my other car - NOTHING since I did the installation myself.