I doubt any kind of an exhaustive study has been done on the benefit of an 8-point over a 6-point socket for that type of repair. I've done a 6-point socket repair several years ago, and it is still holding up just fine as far as I know. That said, I don't know what kind of use it gets.
Another option is to weld up the shaft and cut new splines - I've had that done before also. If you go that route, make sure you weld up the ball in the center of the shaft, or else it will leak when it goes back together. Don't ask me how I know that.