Hello Sanna,
The most important consideration by far should be the requirements of the programs you are applying to. That said, here is a basic comparison of the exams in terms of difficulty:
GRE Quant < GMAT Quant
GRE Verbal > GMAT Verbal
GRE Essay > GMAT Essay
Obviously, there is no comparison point for the Integrated Reasoning section of the GMAT. Anecdotally, most higher end MBA programs tend to put a higher primacy on GMAT scores, and within the exam on Quantitative section scores, but that said each admission process is unique. If you have not already, I would recommend using the GRE official conversion tool <
https://www.ets.org/gre/institutions/ab ... rison_tool > as a reference. Provided your score was equitably distributed your result would be approximately a 660 on the GMAT.
All things equal, and pending your mental math capability since the GMAT does not come with a calculator, I generally recommend students applying for business school use the GMAT as their application exam. However, for students where verbal ability outpaces quantitative by a decent amount the GRE becomes a viable alternative, provided target schools accept the score.
Hope this helps, and please feel free to reply or PM with any additional questions!