I wanted some protection for my differentials. I looked around quite a bit. Some are designed to protect your diffs by putting a cover over the front. Others put a slider underneath so you slide over rocks and stuff (with these kind you generally lose a little ground clearance). I decided on the ones from Four X Doctor because the are the slide over ones, but you don't lose any ground clearance.
I have to say that part of the appeal for me was that you don't really notice them. I like subtlety. I love stuff that works and isn't noticed.
I ordered these for the front and rear before I knew I was going to get a Dana 44 rear end. The people at Four X Doctor were very nice and exchanged the one I bought for my Dana 35 for a Dana 44 version free of charge. You really appreciate a company when you make a mistake and they bail you out. Their products seem super and they are great people to deal with.