You can go to http://schools.ajchomefinder.com/compare_schools?choices=660
which shows a side by side comparison of the schools you specifically mentioned. You can also see the rankings of all high schools in Georgia by clicking on http://www.schooldigger.com/go/GA/schoolrank.aspx?level=3.
I personally moved from North Fulton where my daughter who graduates this year went to Chattachoochee to an up and coming area this year at the border of Gwinnett and South Hall. She is still attending a school of excellence. We made a decision to make a move for investment purposes to get in early on an area that is just beginning to blossom. We did not feel our daughters education would suffer. My daughter loves it. She is still graduating with honors and it has not affected her entry into college.
With all that being said, if you main priority is schools and making sure your child gets in the best high school possible based on rankings then you purchase in that high school district even if it means buying less home for the money. Lets take Walton High School for example. The High School itself has maintained and increased property values in its district. People will buy an older smaller home for the money to place their child in that school.
So resale value is affected by the schools to which the home feeds. Good schools help maintain value and help values increase. Most of the schools you mentioned are neck in neck with each other in rankings. Gwinnett will certainly give you more home for the money. Both North Fulton and Gwinnett offer a lot of recreation but I do feel that Gwinnett parks win over North Fulton parks. Depending on where you work and your desired commute than you may want to look at some other schools in Gwinnett also that are good schools with great neighborhoods feeding to them.
It would be my pleasure to assist you with your home search. As a native Atlantan who grew up in East Cobb, who lived in Alpharetta for 10 years, who now lives in the Gwinnett area I have lived, played, and continue to work both areas.