well you are going to need something somewhere, so thats a given.
What I can say from personal experience is to NOT go with cheapies, but known models that don't go out of adjustment. I made this mistake on a bike setup and it took me a while to figure out that it was them, and not other stuff going on, so in other words, I wasted time and had sometimes dodgey shifting going on during a trip (Im a touring guy).
With proper placement, I see no downside to using them, if you are asking a very general question.