I am looking to tank operations with either a Sin or a Jugg. Is there a substantial difference in ability between the two? I suspect either would be fine for most things, but for hard modes and eventually nightmare modes, I want to know if there is an overall advantage between them in 2.8.1 Thanks for the help.
The answer is always going to be to pick the one you like the most. If you enjoy the class and put in the practice, you'll excel. I myself prefer Juggernauts.
That being said, don't pick an assassin unless you're sure you'll be good. I can count the number of good assassin tanks I've met since 2011 on one hand. It's really weird that the most skill intensive class attracts so many bad players.