I use Rodinal a lot, and HC-110, and I have used FG-7, though not lately. Rodinal's strengths are good sharpness and excellent, long tonal range. Regardless of developer, the price of high sharpness is more prominent grain, by and large. Still, Rodinal is one of the best developers I've seen for tonality and good edge effects. I use it at 1:50 or 1:100, but never 1:25; the higher dilutions are where it really shines, although the dev times do get long.
HC-110 is good, particularly at higher dilutions for low grain, but you pay a little in sharpness. My only experience with FG-7 is slightly odd and very specific. I had a client who requested that I run his HP5 in FG-7 mixed with a 10% solution of hydrogen peroxide. As I recall, the film looked really good, It had excellent tonality and good edge effects. The hydrogen peroxide seemed to contribute to the edge effects, but I don't know how it affected the grain. Development time was around 7 minutes, if you want to try it. It was my first experience with HP5 (a film I now use regularly) and my only experience with FG-7, which I have not used otherwise.
(BTW- the photographer was/is a Magnum photog., and the instructions came from his own processing, which he would occassionally farm out to me when he was really busy. He's been at this a long time, longer than me, and I trust that his addition of h.p. was not some complete wacko idea, but decent chemistry. Unfortunately, I never followed up on it, so I can't tell you much about why he would do it, or exactly what it does- can anyone here shed any light on the subject?)
