SA's sculpting is symmetrical, which is to say row 2 and row 4 have the same exact angle, but in the opposite direction to each other, sort of mirroring one another. This, for example, is why NORDE kits don't need to supply a dedicated row2 "Z" key; you just use the base kit row4 "Z" key rotated around 180 degrees.
MT3 is based loosely on IBM's old beamspring keycaps, which means no two row profiles have exactly the same height or angle, something that Cherry/OEM-profile users are accustomed to. However, unlike sculptured cylindrical sets, MT3 offers a truly flat row profile, row5, for people like me who want their bottom row to be flat like SA row3.
The texture of MT3 is basically the same as DSA (PBT). It has the feel of soft pumice, which is very pleasant.
MT3 is also noticeably thicker than SA, which gives the keys a slightly deeper sound during use. I also find that the stems provide a tighter fit than SA, which means I get less wobble than SA, which is pretty nice.
The one major drawback to MT3 is the lack of support for double-shot (ABS) keycaps. However, I do believe they are working on rectifying that.