some say menthol cigarettes are less harmful,
Who says that? If anything, they're more
harmful than regular cigs. Anything chemical that's added on to pure tobacco is going to increase the risks and menthol, as it's applied to tobacco, is a chemical substance.
Thing is, if you could get a cigarette made from just plain home-grown tobacco, without any of the junk that manufacturers add to "enhance the taste", you'd probably have a reasonably safe smoke. (Nothing's totally safe.) But once you start adding **** like menthol, the more you add, the more harmful the smoke gets.