Alvin,
HooYaa did an A.T. Section hike in 2012 with the Vapor Light 2. He has a journal here on TrailJournals so you could e-mail him and ask what he thought of it. Might give you an idea of what to expect from the “1”.
I think the Vapor Light 1 would get you up the Trail just fine. However, the Seedhouse SL2 weighs the same as the Vapor Light. It is also a quality tent, but would give you room for your equipment (pack) also.
Depending on the year, it can get very wet on the A.T. … and it can be nice to bring your gear “inside” and fuss with it while it’s pouring outside.
Not much help here, but something to ponder while wandering around REI! 
Have a great hike! Bison, AT '09
_Bison_