Amibroker AFL... What's the difference?

Hello all,
I have tested the below two sellif statements (separately)...otherwise the code is identical in the Amibroker AFL. What I am trying to understand is why the back test result is substantially different using the two statements. Obviously they are processing the exit conditions differently...can anyone explain the process or logic differences between using IIF vs OR as below?
//exit trigger
sellif = Cross(MA(C,370),C) or array1 or array2 < 25 ;
sellif = IIf(Cross(MA(C,370),C), 12, IIf( array3 < 25 ,14 ,0));

Thanks in advance...
Steve C