Material and build quality, perhaps. Not to mention the cut, feel and fit, which is a major factor for me when buying jeans. Blnts and AE (never had Old Navy jeans, so no comment) for example are very rough, bad stitching jobs (from the ones I owned), and aren't all that well fitted in my opinion. I've never had a pair of jeans from those places last over 6 months before ripping up, de-threading, or fraying beyond belief.
On the other hand, I've had a pair of Analog jeans for 4 years (keep in mind I'm fairly young), and aside from very minor fraying on the bottom, they're in *great* shape still.