Marc,

Thai food definitely uses peppermint, and I have also seen peppermint
used in Middle Eastern food as well. But it also comes down to it
being your food, and part of cooking is using what you like. So if you
like spearmint, then spearmint it is.

One problem with spearmint is that the leaves are thicker and woodier
than peppermint and many other mints.

Ken