I think that they both have their place. As a kid, I could always spend hours and hours looking at road maps and never get bored! Still love maps to this day.
I like the interactivity of GPS and like oldbuddy said, using Waze to be alerted to traffic issues and such is great. I also like the ETA functionality of a GPS. But I've run into problems with using GPS as well - sometimes it CAN be wrong or lead you to not quite your final destination. Also several times I've run into issues where it lost the signal and took longer to 'find' it than I had time available to me.
Those issues can be quite harrowing if you don't have a paper map Plan B.