I own a DC 3 and have tried the F-30 in stores as well as studios. They are very similar amps, and both work well at low volume settings, but to my ears the DC 3 is a little warmer sounding with the overdrive kicked in. The F 30 seems to be a bit more brittle, which some players may really like - it has more of a sizzle to it. On clean settings they sound basically the same to me - very good. One other point to think about is that the DC 3 has the graphic eq (mine is currently giving me a problem - see my post on that - still looking for help). The graphic gives you a lot of control over your sound at full volume as well as low volume.
Basically though you need to try both and see which suits your tastes better - either way they are good amps, there's no doubt.