There's pros and cons for both cases/manufacturers in my opinion. For all out protection, I believe the Ballistic has the upper hand with the extra padded corners. But the Defender isn't a slouch.
The Defender is backed by Otterboxs great customer service and quick warranty replacements. So that's a plus. A negative is that the outer rubber case seems to fall apart on many Defender cases I've seen. All were for iphone 4 or 4S' however. The Commuters may not offer as much protection but with the hard plastic on the outside they seem to be much more durable. Also, the screen protectors are glued to the Defenders so no easy replacements if they get scratched. I wouldn't think scratches would be covered under their warranty either.
As for Ballistic, warranty/customer service is unknown but they do have a 1 year warranty. Reviews seem to be good for Ballistic cases though. I personally like that the built in screen protector is removable/replaceable and that the hard plastic is on the outside.
If you couldn't already tell, I bought the Ballistic SG Maxx. I just think it looks better and will offer better drop protection. However, I also ordered a Otterbox Commuter. The Commuter will be my go to case and the SG Maxx will be when I'm working for my father's cabinet business with tons of saw dust and going to the beach.
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