GMX or TTSX?
If you have your heart set on shooting a mono then either of them is fine.
The GMX loads don't use special load data (if you are loading your own) - the composition is a little different than the TTSX's but they both require higher velocity impacts to properly expand.
But, because they retain weight better, as suggested if you would typically use say a 150 grain cup/core that maintains 70% of it's weight (105 grains) you can move down to a 110 or 120 grain mono, keep your speed up and since they retain 98-99% of their weight you are still in the ballpark.
Barnes parent company is the Freedom Group (who also own Remington/Marlin) - run by shareholders - shareholders only care about "return on investment".
Hornady is still a private family company - family companies "usually" understand that providing the best product possible for the customer is what keeps them in business.
For that reason alone I would choose GMX over TTSX...