Personally, I'm siding with RT, I have used both tactics many times. I've noticed with a single size #4 you have a lower % of hookups. Yet adding the second hook, jumps your odds up a bit (hookup ratio) having the "stinger" hook, there are many times you have the stinger hook save you. But being lazy, I've honestly had as good as if not better hookup-land ratio on a single size #2 with 8 pound ultragreen leader about 4-5 feet long. The only time I see the double hook as a advantage is if you want to add color. But with good bright eggs, even then I think it is more a mental than anything.

In my opinion the offset of the hook is more important than the size of the hook. Which leads to why a single #2 is better than a single #4. Perhaps using two #4's takes the advantage away of a single #2's offset.
Keith