Is permanent brown less damaging than blonde

If going a darker shade, you should only use a 10 volume developer max.  If going lighter to blonde, you may need to either bleach, or use a higher volume of developer, like 20, 30 or even 40 (depending on how light blonde you want, and how dark your natural hair is....its best to use the lowest volume you can get away with and still get what you want).  Higher volumes of developer lighten the hair, and they contain more peroxide to do so, which is more damaging.  So, if you use the lowest volume of developer you can when you go brown, yes, its better for the hair if you go brown.