I'm tempted to say "you're talking in the context of casual content, so it doesn't matter."

However, I'll put in my two cents: Always be prepared to MT. Yes, that does mean I am telling you to keep your stance on at all times, but be prepared to MT for whatever reason. Do not let yourself think you'll be off-tank. In the realm of casual content, if someone else is MTing, they're very likely to die at any time, so it's a good idea to be 2nd in aggro. Though, be prepared because you may also rip aggro and become MT by default.

If you take aggro, you're doing more damage. To save everyone the trouble, simply put if you're dealing more damage you deserve to be taking the wheel anyways.