Well, if you look at a raw foveon image in it's raw state, it has very little colour and needs some very strong calculations in the colour matrix to make it colourful, whereas bayer cfa images only need a slight matrix, usually adding just a bit of saturation to get a very colourful image. I think that shows that using silicon as a colour filter is not the best of approaches if colour accuracy is your goal.
If you look at either "set" of data in their raw state, neither have color. The readings are voltages proprotional to the number of photons absorbed. The CFA model gets the color from the fact that a pixel is covered by a "green" filter, so it must be 210 worth of "green". It then borrows values from it's red, blue, and green neighbors to get the color.
In the foveon model, the same thing happens for a "pixel", except the photosites that are used to interpolate the color are all spatially co-located. That's a good thing.
If color accuracy is your goal, you should shoot an appropriate target under lighting conditions that you will use, process the RAW files in a way that you deem appropriate, and then measure the results. The Sigma cameras do pretty well.
Another piece of misinformation is:
Also, bayer cfa cameras generally have much much more resolution than foveon is capable of, so even if you have to downsample, you're still ending up with a larger image.
First, a sensor doesn't have "resolution". It has pixels. It's an important distinction. In addition, while it's believed that Bayer sensors are near their limit of usefulness pixel density (let's say 16-20 MP for a full frame sensor), Foveon sensors aren't. If you have a few million dollars (I'll toss in a few as well), I'm sure that Foveon would be happy to crank out a FF sensor based on the current pixel pitch would give you a 14.2 "MP" sensor (which would be called a 43 MP sensor). There's nothing inherient in the technology that limits them from doing that. It's a lot of data to push around, but they had a 48 MP (16 x3) prototype chip in 2000.
Currently, you will end up with much more x,y pixels if you shoot a 5D than if you shoot a SD14. The pixels in the 5D are not as high quality however---there are tradeoffs. B&W resolution will definitely be better with the 5D. Acutence will always be better with the SD14. Color resolution will be better under many situations with the SD14.
Interesting to talk of mush - that's just how the human eye sees things - they get blurry and indistinct as they go into the distance. We don't see false aliassing detail as things get small. We see straight lines as straight lines, not stair-steps.
Indeed, it's really interesting to talk about visual perception and how the eye works. The eye has amazing dynamic range, the ability to pick out fine detail, and a great processing system behind it. Even with a crappy lens! (As an aside, I had my eyes checked and dialated about a month ago---talk about CA with a wide open lens!!!)
One of the things that Foveon does very well is to hold fine detail, even if it's "false". Fine hair in portraits. Fishing line from a fishing pole. Fine fabric detail. The stairstep issues that are often brought up are normally not issues in printing---you don't see them under 99% of the conditions. Where they are issues, one can selectively blur in your favorite tool.
Compare to CFA images---they're non-selectively blurred by the AA filter, and then again by color interpolation. That's one reason for Bruce Fraser's immensely popular sharpening treatise---to regain some of that lost acutence. The reason I love the SD10 (and the SD14 that I've played with) is because making big prints is so easy compared to CFA cameras. The workflow is much easier. And I personally think the prints are better.
I'm not attempting to talk you out of your favorite brand of camera---but there are inherent differences in the Foveon technology that make it superior to CFA systems as a capture technology. This would be equally (or moreso) true for any full color systems. Scanning backs are terrific. 3-chip cameras are too. And perhaps Canon, Nikon, Dalsa, Kodak, or Sony will come out with something full color in the future---but right now, the x3 chip is the only game in town.