Welp I have no idea about combined use. For me it's either or. I may carry both but for dedicated navigation in an unfamiliar area my GPS is the go to device. It's what it's designed to do, not a multi purpose device like a phone, which should ultimately be used as such IMO, a phone. My GPS much more rugged than dainty cell, even with a cover. When things get wet, my GPS will be fine, phone maybe not so much.