There is a very nice thread at
http://www.racketboy.com/forum/viewtopi ... 52&t=46303 attempting to document differences between SNES revisions, I think he is right on when talking about the color bleed/ghosting to the right on the original consoles, seems to describe my original model RGBs problem almost perfectly. Strange thing is, mine does no such thing when using Svideo, which is why I think this kit might be the ticket for the best PQ out of the console.
Why do the pre-1CHIP consoles have a softer picture? Well its due to Color Bleed. You might be thinking "What, even via RGB"? Well the answer is, yes. Many have noticed how the colors of pixels bleed to the right, and this is what's making the picture look softer (some call it ghosting, but its not the same thing. Ghosting is "signal reflections" and is not innate to the PPU)
While the reason for the pixel bleeding is currently unknown, its possible that the DAC (Digital-to-Analog Converter) is causing the distortion. It could also be the transistors after PPU2 (or a combination of the DAC and Transistors). I myself use to believe that Nintendo intentionally added mild bleeding for the purpose of blending dithered patterns, but I honestly do not know for sure (Side Note: Sega's Genesis has pretty poor Composite output, which caused massive color bleed. They took advantage of this by using tons of dithering, which would create new colors and fake transparencies. See this link for more info).
I disagree that there is a discernable frame rate difference in Star Fox though. Even with quick play throughs on both consoles of the the entire game looking for anything at all, I could not notice any difference. If there is a difference, perhaps its so miniscule you'd need a Digital Foundry type frame counter to see it.