I had 162Q 168V Not a great math day.
I have not yet taken a practice test, but I almost always get a better relative score if people think the test is more difficult.
When I look at the conversion charts, a 330 GRE equals about a 700 GMAT. A 330 GRE comes out to about 99th percentile on charts I have found, while a 710 GMAT comes out to about 90th percentile... so, as far as I can tell, you probably should take the GMAT also if you are applying to a top business school?