5' (not 10') squares for indoors - BTW I think thinking in 5' scale seems to create much more plausible dungeons etc than 10' scale does, you get far fewer 180' chambers.
After a long time hexless I'm coming to re-experience the joys of hexes for overland mapping, thanks to the free Arr-Kelan mapping software I use. Scales I like for hexes:
For my game world Ea
100 miles/hex - continental scale
50 miles/hex - chunk of continent with major nations
10 miles/hex - the largest 'local' scale, suits high-level adventuring; can feel cramped though
5 miles/hex - a nice organic scale for lower level adventuring, feels far more spacious than 10 m/hex
1.5 to 2 miles/hex - for local area mapping of what's around your castle
100 yards/hex - tactical battlefield scale
Edit: For my Wilderlands campaign I'm using the published setting at 15 miles/hex rather than the official 5 miles/hex - the world was designed originally at 15/hex and it shows.
15/hex is similar to the 10/hex I use for my homebrew world, with similar benefits. It worls much better than Greyhawk's 30 miles/hex, which I don't like at all. I also think Mystara's 24 miles/hex is too big for a local-scale map and too small for a general campaign overview map.