Apple's Q1 Mac numbers were either very good, or terrible

Apple had either a very solid first calendar quarter of Mac shipments in the U.S., or one that was quite bad, depending on who you listen to.

A dueling pair of PC shipment reports from market trackers IDC and Gartner put Apple's Mac numbers in the U.S. at odds. IDC says Apple's shipments in the first three months of the year were down 7.5 percent from the same quarter last year. Gartner, on the other hand, says Apple's Mac shipments were up 7.4 percent.

So who's right? We'll know when Apple reports its results for its second fiscal quarter April 23. That quarter went through the end of March, and several Wall Street analysts have already warned of a year-over-year decline in global Mac sales (which are different from shipments). That's a metric that isn't tracked by either the IDC or Gartner report.

Complicating matters was a recent report from the NPD Group late last month that suggested domestic (not global) Mac sales were up 14 percent year over year, fueled by iMacs, which were in scarce supply at the end of last year.

According to IDC, part of the reason for Apple's downward drift was cannibalization from iPads. That's nothing new for Apple's Mac business, and something the company has actually been positive about. "If we don't cannibalize it, someone else will," Apple CEO Tim Cook argued to an audience of Wall Street investors in February.

Regardless of whether IDC or Gartner is correct about Apple, the firms agreed that the Mac maker fared a whole lot better than Hewlett-Packard, which remains the top dog in shipments but not in growth. IDC had the HP's shipments down 23.7 percent, while Gartner reported a slightly less severe dip of 23.3 percent.

You can read more about the reports here.