well i think GOD means the creator , while Allah is one of his names -for us the muslims- ,
then for a muslim there is no big difference , because muslims believe that there is only one GOD ,
and a muslim conclude that using his mind , if you look around you , you will see the harmony and order of the universe can't be achieved by just chances and randomness , and there is a creator for all that.
it is also unfair to judge Islam like christianity , because there is a major differences between them , if someone wants to know about Islam , then he just should read about it.