Of the two, Subway - I like the variety of options. I also don't want my bread crunchy toasty and have never really had a couple of terrible service experiences with Quzno's.
However, my favorite subs are from Firehouse, Jimmy Johns, or Earl of Sandwhich.
Subway hands down. Not only is it the healthier option (if you want it to be) but they sponsor one of the local running series and I like to give the sponsors the business so they keep doing it.