Frank Porter Graham is a Dual Language Spanish Immersion magnet, so if that's something you want, it's great. Half the instruction is in Spanish and half the instruction is in English. I'm pretty sure they try to keep the enrollment to 50% native Spanish speakers and 50% native English speakers. I know the principal there, Dr Bivins, and I really like her. She used to be the principal at Carrboro Elementary where my 4th grader is. I have no doubt that she is also doing a great job at FPG.
Northside is brand new and while there was some complaining about the redistricting necessary when a new school is built I have not heard anything negative about the school, itself, at all. It's a great building, gold LEED certified, and the limited feedback I've heard from the community on the school has been positive.
Magnet schools are new for the CHCCS district. Previously you went where your neighborhood was zoned. Now if you apply for a magnet program at FPG, Carrboro Elementary (which also has 2 tracks of Spanish dual language) or Glenwood Elementary's Mandarin dual language program, you may get in. If you don't you go to the school your neighborhood is zoned for.
This is true for CHCCS only. The different school systems in NC may do it all different ways, so I think there are different procedures in Wake Co (Raleigh), which is a huge system.
You can look up the non-magnet school assignment for the house you're considering on the CHCCS website,
Chapel Hill-Carrboro City Schools - Homepage .