In the US it is more common to use 10 to 20 % nitro. Engines sold in the US (not sure if that's on all of them) have usually a shimmed head to lower compression for higher nitro contend commonly used.
In our hobby store the glow fuel has a minimum of 10% nitro and the 15% version is just a dollar more per gallon ($24).
Nitro is probably cheaper in the US, thus the higher use.