I've been running a Gopro Hero 3+ Black mounted on my helmet's chin bar for a couple of years now. The camera is pretty decent but is lacking in features compared to others on the market. However, I do think it has the best audio out of all of them. If and when I decide to replace it I will probably be going for the Sony. As for the mount, the chin position is by far the best location IMO. It gives really good rider perspective and it is less likely to get caught on a branch or broken off.
I ride with mine even on the mundane rides even though I might not necessarily be recording everything. You never know when you might catch a rare animal encounter, your buddy doing something stupid, or run in to a nasty fellow land user, land manager, or LEO that a video recording would be entertaining or save your bacon. If I record nothing of value I just delete them and I'm ready for the next ride.