By Katie Marsal

Published: 01:00 PM EST

Taken at face value, the specifications tied to Apple's most recent MacBook Air updates imply the latest pair of ultra-slim notebooks should handily outperform their predecessors, but a new report claims this notion only holds true for the slower of the two models.

Introduced earlier this month at Apple's annual developers conference, the new MacBook Airs come in two models: an entry-level $1,499 model with a 1.86GHz processor and 120GB hard drive, and a high-end version for $1,799 that sports a 2.13GHz Core 2 Duo processor and 128GB solid-state flash drive.

As part of its review of the new models published this week, Macworld compared the notebooks to their predecessors introduced last October: a 1.6GHz model with a 120GB (then priced at $1799) and a 1.86GHz version with 128GB solid-state flash drive (then priced at $2499). The results? Perplexing at best.

While the new low-end 1.86GHz model bested its 1.6GHz predecessor, outperforming it in most tests and recording a Speedmark score of 11 points higher at 156, the same couldn't be said for the new high-end 2.13GHz MacBook Air, which achieve a score of 175 -- a full 4 points lower than the previous-gen 1.86GHz model.

"What’s weird about the new high-end MacBook Air model is that although it cost dramatically less than its immediate predecessor, it was also slower than that model," wrote Macworld's editor, Jason Snell. "The late-2008 1.86GHz MacBook Air was faster than the new top-of-the-line model in 11 of our 18 tests, and as a result, the old system’s final Speedmark score was slightly higher."

Snell also reported that he saw several cases in which the new, low-end MacBook Air, with its slower Core 2 Duo chip and hard disk drive, outperform the high-end model and its sold-state flash drive. He notes that this may be the result of hard drives being known to outperform their solid state drives in certain operations, but added that the slower system also beat the faster model in some video compression and 3D rendering tests.

"We’re not quite sure why this is happening, though it’s possible that the Air’s thermal-protection systems are aggressively ratcheting down the speed of the faster, hotter processors when they’re asked to perform those tasks, slowing their performance," he wrote.



In light of these results, it's worthwhile to note that several Apple authorized resellers maintain inventory of the previous-generation 1.86GHz MacBook Air, which they're blowing out at $1,649, roughly $150 cheaper than than the new 2.13GHz model they appear to be outperforming. This includes AppleInsider sponsor MacMall, whose own back-to-school promotion offering a free Olympus Stylus 1040 10.0 Megapixel Digital Camera with Mac purchases includes the MacBook Air.

The lowest prices on current and former MacBook Airs are available every day in our Mac Price Guide.