I like both - the stripes give it a lively look while the purple has a softer, subdued effect.
I think it would depend on how large the quilt will be.
Could you do two borders - a small and a larger.
If so, I would use the stripe in the smaller of the two borders and the purple in the larger one.
I would also try in incorporate a pink into the quilt blocks to pull in the pink in the stripe fabric.
Hmmmmmmmmm!!!!!