I guess the benefit to gutting rather than pulling is that it does help cool the meat, reduces carrying weight, keeps the meat cleaner, eliminates stomach acid from leaching into the meat. This is the preferred method if you're going to pluck the whole bird. If you're just going to breast it anyway, just keep a couple of sandwich baggies in your vest to put the breasts in (with attached wing, of course) to keep them clean.
Why is that?
By law you need to be able to ID the brirds... And leaving a wing on is the easiest way to do this.
on a side note...
http://www.youtube.com/watch?v=6OSt...howa.com/youtubemovie.shtml?movie=6OStX_wrWGg
I asked this question last year as well. I still haven't found a good quality knife with the birdhook. If you found one, please let me know what flavour it is.