I'm a Notre Dame AROTC grad (did my AD time and then went back to ND for law school), and my father was a WP grad (and career Air Force), so I think I have some insight into this question. One disclosure, though -- I'm middle-aged, and my dad would be 89 if he were still alive. This said, my dad believed that an ROTC scholarship was a "better deal" than SA, although this was in an era when all ROTC scholarships were full, which isn't so anymore. But you wrote that you have been offered an ROTC scholarship to ND, so I assume that's a full scholarship. If so, that will likely help your admission to ND, but I digress.
I have a couple of other thoughts. If you are a serious, academically-minded Catholic, it's tough to beat ND. In my admittedly biased opinion, no Catholic university balances academic prestige and serious Catholicism nearly as well as ND. On the other hand, if you are thinking seriously about a military career, I'd lean WP. While ND is highly respected among the officer corps, the ROTC numbers overall at ND are way down from what they were in my day (mid-80s), which makes me a little suspicious -- generally speaking -- that ROTC still holds the same degree of stature at ND that it used to in Fr. Hesburgh's day. This may also have something to do with what many ND alumni would observe about ND over time, that it has become less of a school for upwardly striving middle-class Catholics (who were great, natural ROTC candidates) and more of an academically elite school for wealthy Catholics (who aren't particularly interested in military service).
Finally, in the long run you can't go wrong with either school in terms of career options and opening doors.