1. An electro-optical inspection method comprising: imaging at least a portion of a semiconductor wafer, wherein (i) the wafer includes at least two regions, including a first region comprising a plurality of memory cells of a first type and a second region comprising a plurality of memory cells of a second type, and (ii) a repetition vector of at least one type of cells is different from a repetition vector of at least one other type of cells; accessing data that defines at least one repetition vector for each type of cells; and inspecting each region using a cell-to-cell comparison method based on data including the at least one repetition vector for the type of cells in each respective region.