I use RF where possible. I love RF on the Sega Genesis.

My breakdown of some consoles and their hookups:

Atari 2600: One of those doodads to make it hook up to RF the sane way
Master System: RF
NES: RF, unless I happen to be going composite into a 1084 monitor. Both look the same honestly
SNES: RF with the audio going to a stereo
PCE: Composite
MSX: RGB. Anything else is terrorism.

hell, I used RF on playstation saturn and dreamcast for like 2 years. Everyone makes fun of RF. I think it's pretty damned fine lol.

I don't bother modifying my systems for SVIDEO and crap. Too much work for something mundane. I'm not going to remember the 5% increase in video quality after I stop playing and go do something else.