This response may be a bit too late for you, but take a look at this link from Boston Magazine; http://www.bostonmagazine.com/best-schools-in-boston/index.html
Schools are ranked with MCAS scores. Wellesley is #11 with 4,900 students and Newton at #12 with over 11,000 students. Newton is, of course a larger city with 2 high schools. Judging from this ranking both Wellesley and Newton will provide quality public education for their kids. I'm raising my kids in Newton and have friends raising their's in Wellesley. And we're all pleased with the quality of education our children are recieving. There's plenty of AP courses and plenty of acceptances to top schools from both towns.
I believe the differences between the two cities is less the issue of quality of education and more the "feel" of each as they are very different from each other. This is, of course, is something that cannot be quantified and can only be decided by you and your family.
There's not really a good or bad choice here but simply a choice! Good luck with whatever you decide.
