In my opinion the most suitable choice depends on one's command on urdu or english.
If one is good enough to memorize and write fluently in english then he must go for english as the recent trend is Islamia is more contemprory/current affairs.
But if one feel the he can attepmt it in urdu easily then go for urdu.
cant say anyting about scoring but I think score depends on the material u write more and english/urdu choice less.