Because of the cable routing, inside mounted thumbshifters must be friction because they need to be reversed, left/right. That said, clicks are pretty great, you should run the expensive Shimano/Paul stuff, or the less expensive Microshift thumbies. And that said, of my three bikes, two are friction and also pretty great, but no inside thumbies for want of the indexing option should my friction fail (just kidding, about the last failing bit, not that other stuff).