The big winner in fourth-quarter 2010 PC shipments, according to market researchers Gartner and IDC, is … the un-PC, Apple's (Nasdaq: AAPL) Mac desktops and notebooks. However, Gartner and IDC don't agree on the details, so let's take a look at both sets of numbers. (The figures in both tables include desktops, mobile computers, and netbooks.)

U.S. PC market share, Q4 2010 preliminary estimates

Company

Q4 2010 Share

Q4 2010 Share Change*

 

Gartner Says:

IDC Says:

Gartner Says:

IDC Says:

Hewlett-Packard (NYSE: HPQ)

29.3%

28.6%

0.2  

 (0.2)

Dell (Nasdaq: DELL)

22.1%

21.9%

 0.2

(0.1)

Toshiba

10.3%

9.8%

 1.9

1.6

Acer

11.1%

8.8%

(3.8)

(3.0)

Apple

9.7%

8.7%

2.3

1.5

Others

17.4%

22.2%

(0.8)

0.1

 

100%

100%

   

Sources: Gartner Research and IDC.
*Expressed in percentage points.

Worldwide PC market share, Q4 2010 preliminary estimates

Company

Q4 2010 Share

Q4 2010 Share Change*

 

Gartner Says:

IDC Says:

Gartner Says:

IDC Says:

Hewlett-Packard

18.8%

19.5%

 (0.8)

 (0.7)

Acer

12.7%

10.6%

 (0.6)

 (2.2)

Dell

11.6%

12.1%

 0.1

 0.2

Lenovo

10.1%

10.4%

 1.5

 1.6

Toshiba

5.7%

5.8%

 0.4

 0.5

Others

41.1%

41.6%

 (0.6)

 0.7

 

100%

100%

   

Sources: Gartner Research and IDC.
*Expressed in percentage points.

Apple's U.S. market-share growth of anywhere between 150 basis points (according to IDC) and 230 basis points (Gartner) only hints at the Mac's impressive unit growth. According to the company's most recent earnings release, unit sales of Macs grew by a whopping 23% year over year in a market that Gartner and IDC say grew by only about 3%. The 4.1 million Macs that Apple sold in the quarter now give the company a worldwide share of about 4.5%. (And no, the data here does not include the 7.3 million iPads sold in the fourth quarter.)

It gets even better. Gartner and IDC say that cautious consumers, combined with competition from other electronic products -- both firms specifically cited the iPad -- put pressure on consumer PC demand last quarter. But consumers are the largest market for Macs, so Apple took share with a premium-priced product in an environment that should have hurt its market standing.

Nice. 

The biggest loser? That would be Acer, which took a market-share hit on weak demand in its sweet spots: consumer spending and netbooks. The consumer may come back, but the shift from netbooks to tablets is probably permanent. 

Asian tigers
What other lessons can we glean from the Gartner and IDC reports? Well, Lenovo and Toshiba were the other big winners. Lenovo's unit-shipment growth was about 21% year over year, not too far behind Apple. Those are encouraging numbers from Lenovo, which has struggled to fully leverage the IBM (NYSE: IBM) PC business it purchased in 2005. In the fourth quarter, Gartner and IDC say Lenovo benefited from strength in corporate demand, ongoing efforts aimed at consumers, and a disciplined approach to region-specific initiatives.

Toshiba's unit shipments grew by 12% (per IDC) to 14% (per Gartner) year over year. Neither firm offered any explanations for Toshiba's modest market-share gains, but a good reputation may have helped. In PC World's latest reader survey of vendor tech support and service, Toshiba laptops ranked No. 3, behind only Apple and Asus.

David versus Goliath
In contrast, PC goliaths Dell and HP led the losers in both desktop and mobile PCs in that same PC World survey. Who was the winner in both categories? You guessed it: Apple. Hmmm … more evidence that reliability and support may affect sales.

Turning back to the Gartner and IDC reports, we see that HP lost worldwide market share in the fourth quarter, with the decline coming largely in international markets. IDC cited consumers and netbooks -- the same areas of weakness that hurt Acer -- as the sources of HP's disappointing performance. According to Gartner, HP did well in the corporate market but suffered from its large exposure to U.S. consumers. Gartner also stated that the Asia/Pacific region "continued to be a challenging region for HP," a disturbing comment given that the Asia/Pacific niche is generally perceived to be high-growth.

Dell's stronghold is the U.S. corporate market, which was a bright spot for PC makers in the fourth quarter. You might therefore have expected Dell to have shown a meaningful U.S. market-share gain. Instead, IDC says Dell lost a bit of its market, while Gartner says Dell barely gained share. According to Gartner, "Dell's weaker presence in the consumer segment meant the company was not affected as much as some other vendors due to disappointing holiday sales." On a more positive note, IDC reported that Dell's "solid numbers in emerging markets helped it to grow slightly above market at 4.2%."

Foolish takeaway
Fourth-quarter PC market-share data offers little to excite Dell or HP investors ahead of their mid-February earnings reports. Their uninspiring outlooks are consistent with their discounted valuation ratios.

Meanwhile, Apple investors debating how far the iPad and iPhone can take their stock should add a Mac comeback to the debate. The Mac's impressive fourth-quarter market-share gains occurred before Apple launched its App Store for the Mac this month. The "Back to the Mac" campaign Apple announced in October, including the Mac App Store, has PC World saying, "This changes everything."

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Fool contributor Cindy Johnson follows the advice of PC World reader surveys and Consumer Reports when purchasing technology. She currently owns no shares in any of the companies in this story. Apple is a Motley Fool Stock Advisor choice. The Fool has written puts on Apple and owns shares of Apple and IBM. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.