Since you seem to be going for throughput stats, you should use Regail's Dagger. Since 5.1, mastery is by far disc's most valued stat, which is why the dagger is better. If you are ever in the need of asking a question like this again, please PM me so that I can help you. You could also go to maxdps.com and go to the disc section. This website is usually correct on which piece of gear is better for the spec, this website also makes it easier to see all of your available options for gear, so that you can compare stats/gem slots/etc. I hope this helped!