Having used both the R4A and R3A, I think I'd have to vote for the R3A due to its beautiful 1:1 viewfinder and ease of focusing ANY of the CV lenses. But let me digress...
I just read Mike Johnson's article in the latest issue of "Black & White Photography" about the idea of a B&W-only digital camera. What a GREAT idea! Basically he speculates that there will soon be one or more B&W-only cameras on the market and he thinks they will likely be capable of producing amazing images. The idea is that since the sensor will only have to deal with the luminance (darkness or lightness) of things, the camera will be freed up to capture an extremely wide range of light... possibly wider than film! 🙂 Now THAT would be "coooool".