For me, I really like both Dwarf origins, with Noble probably a bit more.
Dwarf commoner shows how bad castless have it and provides a unique outlook on the later part of the game, and is one of the few origins where joining the wardens really feels like a step up in the world. Although the ending of the origin feels rushed, a bit deus ex machina, IMO.
Dwarf noble is just amazing all around. So many ways you can roleplay your dwarf, and the origin adjusts accordingly- you can be an honorable goody two-shoes, or a scheming douchebag that is too noble to talk to your lessers. You can refuse to participate in the noble schemes, or play the game of thrones yourself- the end result is the same, but how guilty you join them differs.
As for the least favorite origin, I have to say it’s the City Elf one for me. I just don’t like how one-dimensional the villain is, how little impact it has, considering how traumatic the whole origin can be.
What about tou?
I always go back to Cousland. It makes the DLC better to know I'm ruling in Amaranthine after what that bastard Howe did to my family. Also, I always end up romancing Alistair again, even when I tell myself I'll go for someone else, and being queen is better than being a side piece (and I can't stand Anora, so ousting her is a plus). In addition I think rogue is most fun in DA:O, though that would never be my main reason, still it's a positive.