You can compare WUs with similar credit.
Say, for example, you crunched some 62.xx WUs before you installed the optimized app. In the "your account" page, you can click on "computers on this account" and then on the second column from the right where it says "results online".
That will show you all results your computer has returned recently, along with credit claimed/granted and how long they took to crunch.
That's the only real way to compare, I'm afraid
HTH,
Simon.