OK, so I just got everything in for the SCART to HDMI. Holy SHIT! The upgrade in quality is insane. The benefits of RGM SCART far outweighs any benefits of a CRT for composite.
I tested it out with Phantasy Star for the Master System. I always played this on the Ultimate Genesis collection on 360, because it looked so much better. I remember being shocked at how bad it looked on the Master System after playing the 360. But Damn, does the SMS look good on SCART to HDMI. It rivals the emulation through 360. I can't recommend that converter enough. I honestly, never thought the Master System could look so good.