I would always pick over the ear. Over the ear have both passive and active noise reduction. On the ear like my Sonys, only have active noise reduction. In the ear like ear buds are another story.
I compared both the Bose QC-15 and the Dr. Dre Studio through several tests for a few hours to try to decide which pair I wanted to buy, (I also own an older $80 Sony). My local best buy did not have a demo pair of Dr. Dre so the salesman told me I could buy both of them and then bring back the pair that I didn't want, so that is what I did. Not a difficult choice after my test. Bose wins easily here is my ratings in a scale of 1-100
Sound Quality: Bose 92, Dr. Dre 95, Sony 80
Comfort after 1 hour: Bose 100, Dr. Dre 90, Sony 90
Noise Reduction: Bose 100, Dr. Dre 75, Sony 75
Overall: Bose 100, Dr. Dre 85, Sony 80
The Dre maybe has a slightly better sound because of bass, but it is marginal. Dre are comfortable but much heavier than Bose. Noise reduction is 4x better with Bose, huge difference! Easy decision now.