If your primary source is digital signal, stay with micro display technology (LCD, DLP, LCOS, SXRD) or plasma/LCD. Using HDMI/DVI to transfer reduces the number of conversions and produce better pictures, though not significant with 42" display.
I own both plasma & LCD rear projection (Sony GWIV). For the same reason as Dlstephenson, I did not go for DLP. What bothers me more about LCD is SSE, not SDE. I recently saw Sony SXRD in store and it still exhibits some SSE, but absolutely no SDE. All of the rear projections fall short in color saturation when compares to plasma. Given your screen size requirement, I think it's a no brainer, plasma rules when it comes to color.
I own both plasma & LCD rear projection (Sony GWIV). For the same reason as Dlstephenson, I did not go for DLP. What bothers me more about LCD is SSE, not SDE. I recently saw Sony SXRD in store and it still exhibits some SSE, but absolutely no SDE. All of the rear projections fall short in color saturation when compares to plasma. Given your screen size requirement, I think it's a no brainer, plasma rules when it comes to color.