Stand-alone GPS or smartphone?

Either one can work fine. Do remember that neither one is anywhere near an infallible master; don't feel you should slavishly follow the routing, and don't rely on any sort of a navigation device to always alert you of things like low overhead clearances or bridges with low weight limits.

I generally use a Magellan standalone GPS, but that may more be simply because it's what I'm used to. Google maps, and I suspect other cell phone navigation systems, has a way of downloading map data so you don't need to be in cell signal range to use the navigation (or consume data, assuming you download via Wi-Fi).

I prefer using a cell phone--but there are times when there is no cell signal--in mountains etc.