Updated from 11:15 a.m. EST

Aggressive Black Friday promotional events had shoppers stampeding into stores throughout the post-Thanksgiving weekend in search of savings, but a wide disparity between two shopping reports left investors trying to make sense of the results.

The National Retail Federation estimated Monday that retailers recorded sales of $27.8 billion over the weekend. Total sales, including online sales, rose 22% from last year, with discounters and electronics stores attracting the most customers. On the basis of its surveys, the NRF said the average shopper spent $302.81.

Separately, ShopperTrak said consumers spent around $8.01 billion last Friday, down 0.9% from last year. It said Saturday sales were flat compared with those of last year at $5.4 billion.

"We saw some very deep discounts being applied through the retail space," said Bill Martin, ShopperTrak's co-founder. "When that happens, it's very difficult to live up to last year's results."

Traders were recently erring on the side of caution, with the S&P Retail Index down 1.5%. The index is up more than 6% in November.

Both NRF and ShopperTrak cited a decidedly promotional atmosphere in stores over the weekend, and the differences in their methodology shows who benefited from the bargain-hunting.

The NRF gathered its data by surveying 4,209 consumers about their shopping progress, and the results included those people shopping online and away from malls at big-box discount chains like Wal-Mart ( WMT), Best Buy ( BBY) and Home Depot ( HD).

Meanwhile, ShopperTrak monitors store traffic only in malls, so their results left out online shoppers and many of the off-mall outlets that are growing in popularity, particularly when it comes to promotional events the day after Thanksgiving.

"Value is the key for a lot of consumers this year, and that's particularly true for those shoppers going out in search of big deals on Black Friday," said Scott Krugman, a spokesman for the NRF. "Shoppers out on Black Friday are looking for door-busting deals, so they gravitated towards big discount chains rather than specialty stores and mall-based stores that can't compete in price. But these stores will probably do better as the season goes on and other people come out to shop."