Looked at simplistically, when the flaps are down, the chord line is from the leading edge to to the rear edge of the flaps. Therefore effectively the flapped area of the wing is operating at a greater angle of attack than the tips and therefore theoretically would stall first. In reality though, because the wing has now become in effect a more cambered section and you throw in the effects of flap slots, vortices off the edges of the flaps etc there isn't a simple answer.
Having stalled a lot of types in the process of doing flight tests for magazines, some stall the same flapped or clean, a slightly higher higher proportion do drop a wing more enthusiastically but it is not predictable by just looking at the wing. The whole airflow pattern is I suspect more complex than simple diagrams would suggest.