Originally Posted by
no1mad
Unless and/or until the OP is ready to invest in a rack for each of his bikes (a QR *could* be damaged in a fall), a backpack would allow him to quickly and easily to select another bike should his primary rig be out of commissiion.
Racks are cheap, even the QR ones. I have one $12 rack on my MTB and a $29 QR one for my road bike. Panniers can be moved between them. As for crashing, don't crash. If you do and its hard enough to damage the rack, consider how such a crash would impact a backpack and its contents. So its just a trade off, its always just a trade off.
But it is the OP's bike and commute so its his choice. We are just offering our opinion