im a student now, graduating next month. maybe :p
for the render [XSI] i use a phong then plug the MR ao shader into the ambient. and plug the output of the AO into an intensity node, then plug the outvalue of the intensity in the color.
same thing in maya but u would use a clamp node instead of a intensity node. i get same results both apps use same mental ray renderers version and almost same lights.