In most mystery shops, the client and the business you visit are one and the same. However, in competitive secret shops, the client hires mystery shoppers to visit their competitors. Why would they do this, and is it ethical for mystery shoppers to do competitive shops?
Mystery shops of other companies allow the client to see how their locations compare to the competition. Typically, the same report forms and guidelines are used for competitive shops as for secret shops of the client’s locations so an apples-to-apples comparison can be made.
Some shoppers do not want to perform competitive mystery shops because they believe it is unethical to “spy” on one company for another. My perspective on this is that the shopper is only asked to report on things that could be observed by any member of the public. As in any other mystery shop, competitive shops involve acting as a normal customer and doing things normal customers do: interacting with employees, making a purchase or return, and making observations about cleanliness. There is nothing underhanded or unethical about any of this, even if the report is not going to the company you shopped.
Remember that as an independent contractor you are not obligated to do any particular shop; therefore, if the thought of doing competitive shops makes you uncomfortable, don’t do them. Keep in mind, though, that you may not know that an assignment being offered is for a competitive shop. They are not necessarily identified that way and may just look like any other shop. In fact, they are like any other shop.