Salloum wroteLAU graduate here (not medicine though). Take my word for it, AUB is better than LAU in everything. It wouldn't surprise me if even the janitors are better at AUB. However sorry to say that a 70% average will probably never get you into either medicine program!
Are you sure? According to my knowledge, you can have a preparatory year if you didn't take some of the required courses, then have an MCAT test. They didn't really mention a specific GPA on the LAU website, and the grading in the Lebanese University is much tougher than that of other universities..