I like the tones and grain of Rodinal. It gives my negs the ability to say "PLING" when watching them on the light table.
Furthermore it is easy to use because of the one-shot convinience and the easy mixing (it is not as thick and syrupish as HC-110).
The big deal....a matter of taste. I also use HC-110 and T-Max for faster films, and Rodinal for films lower than 200 (and Tri-X @ 320).