I didn't read through all the posts but first I would say. Shoot RAW, period. JPG compression throws away all sorts of (valuable) information. Color space setting on camera doesn't matter when you shoot RAW but the LCD on the back is more sRGB friendly so I would recommend using that.
Not sure if the Standard, Neutral, Vivid picture control settings in the shooting menu effect RAW files or not. But set that to Standard. If you want to juice your colors do it in post processing. No control over saturation settings sounds stupid scary to me. Keep both cameras set to Standard.
Each camera sensor interprets and outputs color information differently, even sensors in the same model/brand camera. Every printer prints colors differently. Every monitor displays colors differently. Its not unusual at all to get different colors between two cameras, it would be far more surprising if they were a dead on match. You will not achieve matched colors between cameras or any device(s) in your workflow unless you manage color between all devices in your work flow; input, display, output.
If you are post processing in Photoshop Camera RAW or Lightroom build color profiles for both your cameras using the X-Rite Colorchecker Passport. If you have already have a Macbeth color chart use it and go to the X-Rite web page and download their (free) software and use it to build camera color profiles. If you aren't post processing in Lightroom or Photoshop Camera RAW, you need to.
Finally, get a monitor (printer?) calibration tool. As mentioned above I use the Colorchecker Passport to build color profiles for my cameras, I profile my monitor also and I use printer/ink profiles for my Epson Stylus Photo R3000 printer. I use the X-Rite Color Munki calibration tool to profile my monitor and to profile my printer when I use papers other than Epson. Epson has profiles that work great for all their professional series paper.
I know a lot of people scoff at the idea of spending money on color calibration tools. I know a lot of people that are constantly disappointed in the way their colors look on screen and print too. Very few things I have in my photographic arsenal deliver as much bang for the buck as my color calibration tools do. Its sad to lay down thousands of dollars on a new camera/lens, as many of us do, and then live with disappointing colors.
My workflow is color managed from input (camera), to display (monitor), to output (print). I get what I expect every time, the colors and contrast are rich. And, I don't waste any ink/paper on "test prints" any longer.