This depends somewhat on your phone, but with Android you don't need to worry much about the apps they add in, because they're unlikely to actually be running, and if they're not running they're not causing any significant harm (other than taking up space). They won't be slowing your phone.
If one is running and actually doing something you don't like, you can go into application manager and disable it. Do that with caution though because some apps are necessary. The example I give is I signed into NFL Mobile once and then it started sending me messages about game scores I really didn't want because I always DVR games. Since I wasn't planning on using NFL Mobile again, the easiest way to stop those notifications was to disable the program.