First, the number of filters is important, of course, but since the public is not informed of those numbers, one cannot make a choice so simply.
Second, the distribution of filters across the audio spectrum is important and, with XT32, Audyssey has re-allocated them to make more available at the lower frequencies where they are more needed. Note that in the Anthem AVRs, there is a high frequency limit to the correction because the fewer filters are retained where they are necessary.
Third, the advantages of the Pro kit include the ability to edit your target curves and the better measurements due to the calibrated microphone and dedicated mic preamp. The number of filters and number of measurements is determined by the version of Audyssey.
Fourth, there are many sources of detailed information on both Audyssey, AudysseyPro and ARC. The dedicated threads on these at AVSforums is very informative if you can get through them. There have, also, been reviews in magazines and websites. I have reviewed most all of these products in my Stereophile column and you can simply Google the word "Stereophile" along with the product (MultEQ XT32, MulEQ Pro, ARC, etc.) to find the articles.