I find the trouble with my phone is the screen is hard to read in bright light, it isn’t waterproof and has no attachment point. Also I have to unlock it to use it and if I close the case it shuts off to conserve the battery which is irritating.
On the other hand my gps has a bright screen which is always on, is weatherproof, has a clip to attach it to my shoulder strap and a lanyard so it doesn’t hit the floor if I drop it. Moreover, the batteries last for multiple trips and I carry a spare set of AAs in my bag.
Actual maps are a faff; they have to be got out and unfolded before use and then put away again, not to mention coping with them in a breeze. Either that or they have to be prefolded and carried in a map holder which either flails around in the slightest breeze or has to tucked away to the point where you can’t get at it easily anyway. I print out my maps onto A4 sheets, double sided and then put them in a clear wallet which gets folded into 4 and put in a trouser pocket.