If you want to get MBA admission in top busines school/university, which one will help you more GMAT or GRE ?

Neither will help you over the other if you have already locked your target schools. Most schools in US nowadays accept GRE, whereas GMAT is the default.
GMAT is more specific (acceptable) to business schools while GRE has a wider audience.

Candidates who apply to B school with the GRE are signaling to schools that they either have low quantitative skills or are also considering other graduate programmes. GMAT is safer. GRE helps widen the pool, especially in the four semester programmes where students have more support in getting up to speed.

GMAT. There's very little reason to do the GRE over the GMAT if you're only applying to MBA programs.