Own the Transpack TRV--love it. I don't have any experience with Line, but I can tell you that Transpack customer service is excellent. The zipper began ripping out of one boot compartment after almost three seasons use. I returned the bag to Transpack and they replaced it with a brand new bag and did not even charge me to ship the new bag.
I am very pleased and will be a loyal Transpack customer. I recommend them highly.
We sell em both and the LINE pack is not made by Transpack. Both are great bags. Transpack is a smaller company with awesome customer service and warranty. If you go with Transpack get the TRV (a little bigger than the XT1)