I think it depends.
At the moment, where I am in life is I have to work, have kids, live and work in the USA where the holiday time is notoriously bad, so you get the picture: I'm usually very short of time. While in my cycle touring Nirvana it would be lovely to find out I'd taken a wrong turn that may extend a tour by a day but been rewarded with some beautiful landscape or memorable chance encounter with a character, realistically, I'm more like "oh no, I have to get back to right route so I can get back in time....".
So at the moment, when I do go touring, the best option for me would be a pre planned route with a gps that provides turn by turn instructions. Alas, I haven't got one, but this would be my ideal solution. I'd really like it if I could just set off and concentrate on the scenery and enjoying ride, rather than be stopping frequently* to check a map. I find, given my current situation, its frustrating to have to keep stopping to check. I've not got a tour planned this year, but next year I am intending to get a gps that is capable of this for my next tour. Even if I had more time, I still like the idea of not having to stop frequently to check a map!
On the other hand, good maps are great; they never run out power, and they provide a much better big picture of where you are going as opposed to a tiny screen. Plus, you'll never have to wait for them to pick up a signal

.
*to be fair, the signage where I live is notoriously bad, so it does necessitate frequent stops and checks. It's not unusual for roads to "disappear" (ha! Route 57 western Massachusetts

), not be marked at all, or -my personal favourite -for there to be no signs at an intersection, but once you choose (hopefully) the right road, you find a sign about a mile down that tells you where you are. I do think as a whole, most European countries offer much better signage.