TLDR: [Read the title.]
The new norm for RPG maps is the 5' square. This is reasonable in terms of fighting, in fact this little meme is going around the net right now, illustrating a person in a 5' square, and I approve.
I also understand why most battle mats are printed as 1" squares = 5'. One human-sized miniature per square, obviously. I am going to make the argument, however, that when you are drawing maps, a 1" = 10' ratio is more optimal. My reasons are simple:
1) You can fit a lot more map onto a single sheet of graph paper. Which means a person looking at the map can get a bigger scope in one take as well.
2) A four person party can fight within that square in two ranks of two. So if you are using the map in play with tokens or abstract minis, you can just track the party's location with one pawn.
3) If, for use at the table, you blow up the map to 2" squares that represent 10' each, it's super easy for people to draw the extra lines in with their imagination - e.g. position their characters in a corner/quadrant of each space.
That's all I wanted to say. 10' squares. I love 'em. When I'm drawing in my 5x8" dotted notebook with 3/8" between dots, it allows me to draw a whole "level" of dungeon. It also somehow frees me up to not draw all the "furniture," as that would be impractical. I only note the big stuff, if anything: fountains, tables, etc.