Internal candidate in 2nd position (obtain 89% marks) and external candidate (obtained 90% marks). Who will be best for the organization?

I think the difference of1 percentageis not a big deal. If the position is entry level or executive level then new candidate is a good choice. If position is of senior level then it is better to consider the internal candiate as he is well aware of org policies, procedure and environment and wihtin no time he or shae start delivering the results and image & motivation level of other employee also increased.

Well on the spot based on the position and role take ur decision.