I guess it would depend on if/where you wanted to get higher education? I don't know of any U.S. colleges, for example, that request or accept the IGCSE (but then, I'm not familiar with what international students are required to show for education background) but if you are staying in Saudi Arabia or its environs (or Europe, etc.), that might be a good/better choice than the SAT's. If I had the choice, I'd take both better show what I could do or what I needed to work on, etc.

I have both my U.S. State driver's license and the International Driver's license; it makes things easier and provide additional proof of identity! Taking both tests if you can, might help you in a similar way; show your "versatility" better :-)