As much as I loathe quoting magazine articles...
A few years ago Steve Magnante (sp?) did a back-to-back test between a Dana 60 and a Chrysler 8 3/4 rear end (very similar to a 9" Ford) in a Dart with, if memory serves correct, a 528 crate Hemi.
(I searched the HRM and CC sites for the article but came up dry)
Anyhow...long story, short version; despite the fact that the Dana was considerably heavier than the 8 3/4", track testing showed no significant difference in e.t., although I believe the article stated that the car was much more stable down-track, which the author credited towards a better posi unit in the Dana.
IMO, in a Pro-Touring build, I would use a 9" and not lose a moments sleep over it. For a serious drag car, I'll say this...I've seen a
lot of broken 9" Fords, but I can count on one hand the number of broken Dana 60's I've seen.
FWIW, YMMV.
Eric