We had the same dilemna a couple of months ago. We have towed our first three Jeeps for well over 100k miles with no real issues, however, our current Jeeps seems to be a rock chip magnet. So bad infact that this past season we hauled it in the enclosed trailer almost the entire season to save the front end. This however presents its own issues with finding large enough sites and is somewhat limiting to where we can stay.
I looked at both the Protecta-Tow and the Roadmaster Tow Defender. The Protecta Tow is a little less expensive but in the end we went with the Tow Defender.
Here is a link to the installation and review.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27298508.cfmMike.