Those two canvases are very similar. Both have lots of OBA's. I believe SSMC has better Coca-Cola reds and better coverage in the blues and violets than most matte canvases.
Also, the latest batch of 24" SSMC rolls I just got seem to have a different formulation than the older 36 and 44" rolls I have from just prior to that, the new stuff prints notably darker than the older stuff. It was so noticeable I printed my standard test image on both back to back, and sure enough the new stuff is darker than the old on side by side prints. Go figure. Maybe the new batch got coated with the wrong emulsion. If you want a REALLY killer OBA canvas, try Canson PhotoArt HD, it ain't cheap and you need to make your own profiles. If you want a really modest non-OBA canvas try Canson Museum Art. If you want something in-between and OBA free, try Lyve.
The wise thing to do is choose a single media and learn how to get the most out of it. Just getting a print with the right density and best possible contrast is more important than theoretical gamut differences.
