Matt, I've done limited tests of both. To my eye, the two papers are radically different. MGIV compresses the highlights and the upper midtones quite strongly with a very abrupt transition in the middle of the tonal curve, while MGCT maintains greater highlight contrast within a smoother overall tonal curve - it's even a bit reminiscent of the long-gone MGIII Deluxe. MGCT is a better match to an old-fashioned shouldered film like TX, and will probably be a decent replacement for the now-discontinued Agfa MCP.
I very rarely use MGIV RC - I find the highlight compression and the especially the abrupt change in contrast in the middle of the tonal curve to be a poor match to my negatives and my taste. MG Warmtone also provides somewhat compressed highlights, but within a much smoother overall gradation. It would be my choice over MGIV for a general-purpose RC paper if I were working primarily with "straight line" films.