Sweet & Tart Restaurant vs. Cafe on Mott
Having eaten about a million times at each, I would say that:
1) the cafe is slightly cheaper;
2) because the cafe is tiny, the chances of your getting food within seconds of it being prepared are better;
3) but the quality of the non-tong shui items at the restaurant are more than a little higher, e.g. wonderful, satiny jook with dried scallops in a claypot as opposed to slightly gluey jook in a plain bowl;
4) and there is a vast menu of really good stuff at the restaurant unavailable at the cafe.
Advantage: restaurant, especially when ordering a full meal.