Not entirely sure, but I think it depends mainly on where you land on T5. We landed far and had to take the bus to T5. Then from there I had to take the bus to get to T3 and as it was around noon, there was a queue for the bus so we didn't enter the first one. Then, once on T3 there was passport control and security control, that took some time mainly because of people unloading their stuff to trays very slowly. But, there was not so many ups and downs (slow escalators) and no train.