Chip, I think the Delos is a better sounding carty than the Zephyr from the perspective of bass slam, bass definition, transparency, imaging and ability to extract details out of the grooves. But having said that, the Zephyr is a very, very fine cartridge at its price point of $1K, which is $650 less than the Delos.
You asked about which carty is warmer/richer. I suppose the Zephyr wins out there, but only because the Delos possesses the attributes I listed above. Given the choice between just the two carties, I'd go for the Delos, at least based on my initial impressions of listening for 3 or 4 days.
Btw, I own the VPI Classic 2.5 (check my system description). Both cartridges are a good match with the Classic tonearm. When I tried the Ortofon 2M Black several years ago, I didn't have much luck in setting it up. For some reason, I think it has a compliance factor of 22 or more, which makes it a tough match with the VPI tonearm. The VPI is really best suited for low and medium compliance carties.