we can compare the two only for theorycraft purposes, but dont forget rules were different back in the day. There were no weight classes, god damnit. Royce fought guys with A LOT of weight over him. Plus, basically only biting and eye gouging were forbiden.
Royce did great at his time. Maia was doing good up to a certain point and has been great for the past what, 1.5/2 years?
I am a big Maia fan and Im not dimishing his accomplishments by any means, he fights competition A LOT more prepared than Royce did. IMO he is the best grappler in the UFC, and by far. I expect him to be champ if they dont take like 2 years to give him a title shot.
However, comparing these two - from an exclusive fighting perspective, not considering personality, roids, how humble one is or whatever - is no easy task and I would not jump on voting for Maia. Let us wait until Maia history is done then we can do it, I feel like Maia can still shock some people by subbing the champ.