I'll have to disagree with you there. Bill. There's less short grain runout but it's not eliminated. You'd have to do a very long scarf on a short headstock to accomplish that and still keep enough headstock angle, and even then it wouldn't be eliminated because the angled grain is on one piece, not both.
Here's something I copied long ago at a forum I can't remember, it's from an acoustic guitar maker named Grant Goltz:
Now, the theoretical 3,000 psi strength of a glue joint in a scarf needs to be looked at in the proper context. Scarf joints are very common in boat building. I use them all the time. That is how one builds 16 foot long boats out of 8 foot long plywood. To get near the strength of a solid length of wood, the scarf joint needs to be cut at an 8 to 1 angle to minimize the end grain gluing effect. In other words, a scarf joining 1 inch wood needs to be 8 inches long, or on my 3/16" thick boat plywood it needs to be 1 1/2" long. So a 1/2" thick peghead should have a 4" long scarf, but that would only give a 7 1/2 degree peghead angle. At a more typical 15 degree angle, you only get a 2" long glue joint, or a 4 to 1 scarf. Compound that by the fact that the angle is all on one piece, effectively doubling the end grain effect (so do you have an effective 2 to 1 scarf?). In any case, no way in the world are you going to get anything approaching a 3,000 psi joint. Actually, on boatbuilding scarf joints, we would never trust the strength of woodworking glue (ignoring for the moment the non-waterproof fact). Such joints are always glued with marine epoxy, which does actually have strength in the glue.
So, what is the likely bottom line? Obviously both construction methods have been used with success on thousands of guitars. Thus both appear to have adequate strength under normal circumstances. I would be willing to bet that there is not a whole lot of difference in the actual strength of the two. So which is better? I guess, as my Dad used to say "six of one and a half a dozen of the other". Happy building.