I actually had the same thought in my mind when I first started Leatherworking. Even though I'm a druid [also played 60 rogue before] I couldn't make up my mind.
One thing that I noticed when I was looking through the recipes and mats was the fact that Elemental is easier for a rogue to farm since they can kill elementals alot faster than a Druid can, while they cannot kill Devilsaurs as efficiently as a Druid can. I would personally recommend that you would choose Elemental Leatherworking for various reasons:
1. The Gear you can make with elemental is way more useful for rogue. The volcanic set is great for when you're just starting MC, not to mention very easy to make and sell once you have ur own set.
2. Stormshroud, in my opinion is way better overall gear for dagger rogues since it brings up your crit chance very nicely.
3. Like I said before, farming the materials for a Elemental Leatherworking is easier in my opinion with the whole Devilsaurs vs Elementals.
Even though both choices offer diffirent recipes which compliment classes diffirently, I think as a rogue you should choose to do Elemental Leatherworking.