The GameSX SNESjr RGB mod is sort of rubbish.

[NFG]

I read over on RetroRGB that the SNESjr had better RGB output than the original SNES, but that was never my experience.  Turns out the RGB mod I designed when the system first came out was...  sub optimal. 

Here's a comparison of RGB outputs, showing the GameSX SNESjr mod, the original SNES, the RetroRGB mod, and finally the RGB after running through an XRGB2.  It's interesting that the capture from the XRGB is so good.  I suspect the de-interlacing of the XCapture is involved here, my hunch is 240p is its weakness.  The XRGB does a really great job with the upscaling, but I think maybe I've tweaked something at one point because the colour and brightness are a little off.

[Shadow_Zero]

The difference is the "add resistors to the RGB inputs that adjust the brightness" part? (1.2k resistors)