Kenmore is more ethnically diverse and has a higher FARMS rate than Swanson. Its test scores aren't as strong. On paper, to some this means that Swanson is the stronger school. I don't have a child in middle school and haven't yet taken the time to evaluate them all myself yet.
OP, there is a process for transferring schools, but it's not about "convincing" the school system. Requirement #1 is that the school have the excess capacity to take transfers from other schools. Swanson doesn't have that option next year. Here is the APS's website on the topic of transferring between middle schools:
http://www.apsva.us/Page/3014