Ok stole this from a buick site via google- makes a lotta sense:
I see a lot of people running 10 degree retainers in hydraulic or flat tappet applications. This can lead to failure in applications where spring pressure is not high enough to really "lock" the keepers in place properly.
If you are running, say 125-140# of seat pressure, the 10 degree lock will almost always show signs of polishing and chatter. This is because the side load is not strong enough to lock it tight and it's moving around. A 7 degree lock has more locking pressure because it takes the same available lateral load, and turns it into more side load though a lesser angle and more leverage.
Look at it like a door stop. If you give a 7 degree stop the same kick with your boot as a 14 deree stop, the 7 degree will be wedged under the door twice as hard.
If the Crane Super 7 lock is available for your application, you get the benefit of a wider lock, but better clamping force than a 10 degree. It is a great "in-between" lock/retainer set-up for high pressure solid cams that may chatter 10 degree parts.
With springs that have seat pressures in excess of 200#, a 10 degree becomes the preferred choice. When the open pressures are over 550#'s, lock pull through becomes a serious reality and you need to spread the load over a wider angle.
The biggest thing is to look at what you have and identify any problems before they happen. If your 10 degree stuff is chattering and fretted...problems may loom on the horizon.
The reason I bring this up, is that I see cam manufacturers recommending 10 degree hardware, in their books, for even mild hydraulic cams and it just does not work well.
