I too shoot professionally, and did 3 days with the MacMillan Bloedel operation at Chemainus on Vancouver Island (standard gauge 2-8-2t), shooting with a Mamiya C330. I made quite a few 16x20's in the darkroom, from these images, and I can say that the ones done from scans with an Epson 4990, and printed on an Epson Stylus Pro 4800 are at least as good, in many cases better.
The Ektachromes shot in 4x5 of freshly rebuilt Climax #10 of MRSRR, scanned at 3200dpi are amazing! They are also HUGE files, so have a big hard drive if you scan many! These will print really crisp, 40" wide, probably bigger.
Steve