Consumers can use a Visa (V -0.16%) card to shop at warehouse club retailer Costco (COST -0.79%), but should investors buy either one of these growth stocks? The answer isn't exactly clear-cut.Some investors shouldn't own either stock. Here's why one of these two well-known stocks is probably a better buy than the other.What do Visa and Costco do?Visa is a payment processor, which puts it in the financial sector. It collects small fees for facilitating financial transactions via cards that are emblazoned wi ...