I'll pick UM over Perdana.
Firstly its because it has been around for quite some time and there is something that is not quite right with Perdana Uni yet. I can't remember the link but you can check this dude's blog:-
He's well known for his critical insights on our medical education. Look for the particular post on Perdana Uni in collaboration with John Hopkins and Rcsi, I think.
And I am not sure how it is this time. But last year I attended a talk from Singapore ministry of health and *drumroll* they only recognize UM grads and will only take them as houseman/intern. Take this into account, should you have any plan on doing your HO in Singapore lah.
I think that should pretty much explain why I'd pick UM over Perdana.
But no harm done. You can just attend both interviews and see the facilities and faculties yourself. I might be a bit biased as I have never seen this Perdana and most of my friends are UM grads.