I'm probably not the best person to be replying here because my hunter is level 60 and my RK is around level 14.
I don't do a lot of group play in the game but I have done quite a few instances and one raid with my hunter...only with kin members and they've always been happy to accept my hunter to come along. So, if you are looking to do a lot of group play, look for an active kin and you shouldn't have that much trouble getting invited to do some instances and raids.
Yeah, most of the time you don't have to think about what you're doing as a hunter, but me...I like to challenge myself and aggro as many mobs as I can at once so I do have to think about what I'm doing. Even the easiest classes can present a challenge then. If anybody is in the area when I do that, I do get a lot of people stopping to watch me be crazy. And my hunter's a dwarf so there's no escaping for me when I go crazy like that.
I can't say much about my RK because I've been spending most of my time on my hunter because I'm enjoying playing him a lot.
Most people recommend that you try both classes to level 20-ish to get a feel for them.