OK, let's see. There's at least three parts to this problem - theoretical, technical and practical :) Now, the theory tells us that belyash as such is a Tatar word, and is related to a certain sort of Tatar meat pies. It also tells us that it has to be fried; in Russian, belyash is a pirozhok; it is just one of the many types possible. Technically, your picture from zakusochnaya is slightly off, exactly because belyashi would be fried, and a generic pirozhok s myasom would be baked - granted, it might be difficult to see under often non-optimal lighting conditions :) I can also tell from experience that belyashi usually have kind of juicier stuffing, while a baked pirozhok would have drier minced meat inside. Finally, the practical part tells us, iirc, that the proof is in the pudding. That is, I would consider the specimens before me and choose the ones I'd decide are better for me. There is a general preconception that belyash is a "cat-n-dog" pie, relating to the mystery meat status of its stuffing; it also kind of looks greasier and less healthy. But in reality you just take a look, sniff and buy what you like more. Also, you have to take into account the geography. In Bashkiria or Tatarstan I'd take belyash without thinking twice. In St.Petersburg... I would lean towards pirozhki, but consider the specimens laid out before me, as above.