Will it compete with an M-4 in CQB or a match tuned AR-15 on a range? No, but one of its more important attributes is that the SU-16CA version is available in CA, while AR-15's and many other rifles in that class are not. A lot of us who grew up with the Garand and M-14 thought that the M-16 was a POS; now I have a rifle with even more plastic and it works fine.
AR-15's aren't illegal in CA, but there are restrictions on how you can configure it. I can go out to my gunshop and pick one up today if I wanted to. In fact, a majority of the firearms aren't "illegal" in CA, it's just that some are much harder to acquire (legally) than others.