Well, difficult to say~ You could find these branded clothes, shoes, cosmetics as well as wholesale markets in Beijing. It will be much cheaper to purchase these branded goods in Shanghai. However, you could find many local products in Beijing, such as these time-honored silk and Chinese traditional decorations....
You could find special Beijing shopping on this page: https://www.travelchinaguide.com/cityguides/beijing/shopping.htm

Many of my friends that have lived in Beijing say that clothing in Beijing is cheaper.
However, that does not include the real brands.
On-the-street shops are more western-styled than chinese-styled in Beijing than in Shanghai according to them.