Pick a subset of titles form different wikis. Write a script to hit Parsoid/JS and Parsoid/PHP for all these titles and run performance benchmarking for different modes (wt -> html, html -> wt, wt -> pagebundle, pagebundle -> wt, selser with some random edits maybe). The script might use other tools like ab, for example.
This will let us give us a more solid measure of performance comparison between Parsoid/JS and Parsoid/PHP.