Yesterday, IBM tracked millions of transactions on hundreds of retail sites in the U.S. to discover the trends among mobile shoppers over Christmas Day. And the results are rather nice for mobile in general and for iOS in particular.

According to IBM’s report, which is based on the IBM Digital Analytics Benchmark, mobile traffic accounted for nearly half of all online traffic. The highest over this holiday season, mobile traffic made up 48 percent of all online traffic, up 28.3 percent over the same period last year.

As for mobile sales, they accounted for nearly a third of all online sales. Up 40 percent compared to last year, they constituted 29 percent of all online sales over Christmas.

IBM’s data also suggest that while customers browse more using smartphones, they buy more using tablets:

Smartphones drove 28.5 percent of all online traffic compared to tablets at 18.1 percent, making it the browsing device of choice. When it comes to making the sale, tablets drove 19.4 percent of all online sales, more than twice that of smartphones, which accounted for 9.3 percent. Tablet users also averaged $95.61 per order, versus smartphone users, who averaged $85.11 per order.

And now for the big question: how did iOS and Android fare against each other in terms of online traffic and sales on Christmas Day?

Well, iOS accounted for more than a third of overall traffic with 32.6 percent, more than double Android’s 14.8 percent share.

Apple’s mobile operating system also trumped Google’s in driving online sales: iOS accounted for 23 percent of all online sales, five times Android’s share, which is at 4.6 percent. And according to IBM, “On average, iOS users spent $93.94 per order, nearly twice that of Android users, who spent $48.10 per order.”