I have a 60CSx and a 705. The 60CSx is a great unit but not on the handle bars. The bar mount that they sell is not safe. In my half dozen test rides the unit came out of the mount at least once each time and that was on the road not even a trail. If you dont mind carrying it in your jersey it will work great but then you may not hear the turn warnings. Or, you will need another mount that is more secure.
As for on the bike I do prefer my 705 as it is made for use on the bike. If you were to get the 705 you would have cadence also and be able to eliminate your other computers. I also run courses a lot of the time and the 60CSx cannot do that.
That is my short and sweet response.