Between discount and promotion which should a retailer chose generally and why? How do a retailer judge which works better on a lon term basis?

In most of cases retailers choose a discounting not knowing long term impact, at the same time scheduling these in an appropriate time, hence lose on identity getting trapped to perception of customers

A discount pricing strategy is useful for driving traffic and sales short term. Used as a long-term strategy, discount pricing has some negative effects on market position and brand loyalty.Promotional discounts are short-term, to drive sales. Using promotional discounts too often trains consumers to wait for the sale and may damage the overall profitability of the product.