I have stayed at Occidental Grand and Occidental Allegro....both good....Occidental Grand is better in terms of more a la cartes, bigger resort, swim-up pool bar, not to mention best disco in punta cana (a place for locals too). I really liked the entertainment and atmosphere at allegro, but for your age group and price you are probably looking for....occidental grand is a pretty good party spot. Occidental grand is 4.5 star, allegro is 4 star. Occidental grand was actual cheaper than allegro but i guess it was because of the time of year. went to allegro in jan 2006 and then grand in nov 2006.
heard bavaro princess had a fire sometime this year. don't know if damage has been repaired or whatever.
Punta Cana Princess= I hear lots of older people.
Ocean Bavaro = not sure
Grand Oasis = have never heard of
Well you are back by now so hope you made a good choice and had a good time!