I am long GSK, with no current position in AZN due to its massive run up last year I was holding off, now its come back down I am seriously considering it, as Vedran mentions growth wise its a better options than GSK overall, I went GSK purely from a value play (time will tell if value trap 
)
I have price alert at AZN under 6750p, lets see what happens.
Just be aware the dividend will probably decrease in next couple years when the company splits.