They're both unlikely to give much aid b/c u are an international student. As for the schools themselves: Lafayette is smaller, is a LAC rather than a Uni, and excels more in liberal arts (Better for the liberal arts side of econ). Lehigh is larger, does more research, and excels more in trade school type majors (Engineering/Business). It would be better for a more practical, business-y econ curriculum. Because you seem to want to teach economics with the PhD, I'd go with Lafayette.
Another slightly off topic fact, Lehigh has a unfavorable male to female ratio that I thought was noticable on my visit. So if you're a guy, def go for Lafayette.
