The neck also has better drainage in most cases than the rump, so if an abscess forms, it's easier to deal with. If you really have to give a shot in the rump, inject the leg on the *opposite* side from where you are standing. They usually kick with the leg that got poked.
Needles do break on occasion, esp if the horse is fractious. I've had the hub of the syringe break off as well.
Personally, I like the stick-the-needle-in-first approach. It gives them a chance to settle down after that huge horsefly bit them in the neck. :)
Thanks. The neck it is. The scratching and smaller needle really seems to work better. It takes longer to inject the medicine but it doesn't seem to hurt as much. 6 more to go :')