The Norinco CZs are great, no doubt, but the SIGs are a different story. Norinco hasn't been able to manufacture the aluminum quite right in some cases (do a search), leading to premature and extreme wear. Also, the Norinco SIGs do not last nearly as long as real SIGs, according to people who own "range" Norinco SIGs. Remember, this is not a steel 1911 or CZ, this is a synthetic and aluminum SIG copy, so materials may not be up to par as with other products Norinco manufactures.
Why is the SIG 228 so great?
I have only also held a Norinco P226 copy, so I don't have a lot of experience. But the 228 is a great compact design. It has a grip that, while it holds 13 rounds (ideally), does not feel too fat (I don't like Glocks for this reason, or wide 1911s, but the 228 fits just fine. With no room to spare. It is perfect clearance). It follows the SIG design in that it is extremely easy to strip and clean. It resets perfectly on target after every shot. Even my Norinco has never had a single feeding, firing, or extraction problem, or problem of any kind, even using the crappy Norinco mags. The sight picture comes very quickly, and pointing is fairly intuitive.
So it makes the most out of design compromises, and is a very intelligent compact design. The only problem is that recoil is a bit heavy because the slide is so much heavier than the grip (a problem with all the 226/228 series, no doubt), and because it is smaller than a 226 or 1911. It is small enough to be carried all day without noticing it as much as a heavier pistol, however.