What are the differences between the MacBook Air (NVIDIA/Late 2008) and the "Unibody" 13-Inch MacBook (Aluminum/Late 2008)?

Please note that all Macs mentioned in this Q&A have been discontinued. The MacBook Air (NVIDIA/Late 2008) was replaced by the "Mid-2009" MacBook Air on June 8, 2009.

When the original MacBook Air -- affectionately dubbed the "MBA" -- was introduced, EveryMac.com compared it to the "White & Black" MacBook models available at the time and concluded:

The MacBook Air and MacBook are two very different types of notebooks targeting two very different types of users. The MacBook is a relatively compact, relatively inexpensive system designed for day-to-day use by a mass audience, whereas the MacBook Air is a premium product for those who want a beautiful, lightweight notebook and are willing to sacrifice affordability, performance, connectivity, and expansion to save weight and gain style.

Compared to the original MacBook Air, the "NVIDIA/Late 2008" models are effectively the same externally -- with the exception of video out -- and have an improved internal architecture and improved graphics for modestly increased performance, but for all practical purposes have the same comparative limitations of the original model in terms of affordability, performance, connectivity, and expansion.

Meanwhile, with the introduction of the MacBook "Unibody" line, Apple has improved substantially the "consumer-targeted" MacBook, narrowing the gap between the MacBook and the MacBook Air.

Photo Credit: Apple, Inc. (MacBook - Left, MacBook Air - Center, MacBook Pro - Right)

The "Unibody" MacBook models use effectively the same architecture as the "NVIDIA/Late 2008" MBA, but cost less, have faster processors, and superior connectivity (reduced from the earlier MacBook models, but still offering two USB 2.0 ports, Gigabit Ethernet, and optical digital audio in/out, compared to one USB 2.0 port and no onboard Ethernet or optical digital audio in/out for the MBA). Additionally, the MacBook "Unibody" models are about as easy to upgrade as the previous MacBook models (with an easy-to-replace battery, RAM, and hard drive), compared to the MBA which is a challenge to upgrade the battery and hard drive and has 2 GB of non-upgradable memory). The "Unibody" MacBook also has a convenient internal optical drive whereas the MacBook Air requires the usage of an external one or software workarounds.

From the perspectives of affordability, performance, connectivity, and expansion, the MacBook "Unibody" models at least maintain their comparative advantage over the MacBook Air, and the "Unibody" models weigh a half pound less than their predecessors (lowering the gap between the MacBook and the MBA to 1.5 pounds -- 4.5 pounds compared to 3 pounds), and likely most would agree are considerably more stylish and attractive than their predecessors as well. The MBA, on the other hand, uses the same stylish case as the original model.

On even more minor points of differentiation, the MacBook line has surpassed or closed the gap with the MacBook Air -- both MacBook "Unibody" models have an improved "no button, four finger" multitouch trackpad (compared to a comparatively simple "one button, three finger" trackpad on the MBA), LED-backlit displays (that are of lower-quality than the one in the MBA), and the high-end MacBook model -- the MacBook "Core 2 Duo" 2.4 13" (Unibody) -- has the same backlit keyboard as the MBA as well.

These differences are perhaps summarized most conveniently in a chart:

	MacBook Air "Late 2008"	MacBook "Late 2008"
Processor Speeds:	1.6, 1.86 GHz	2.0, 2.4 GHz
Video System:	NVIDIA GeForce 9400M	NVIDIA GeForce 9400M
Video Type:	Integrated	Integrated
Video Memory:	256 MB*	256 MB*
Display Size:	13.3"	13.3"
Backlighting:	LED	LED
Native Resolution:	1280x800	1280x800
Ext. Display:	2560x1600	2560x1600
Hard Drive Size:	120, 128 GB**	160, 250 GB
Hard Drive Type:	Serial ATA	Serial ATA
Default Memory:	2 GB	2 GB
Max Memory:	2 GB	4 GB†
Gigabit Ethernet:	No††	Yes
USB 2.0:	Yes (1)	Yes (2)
Firewire 400:	No	No
Optical Audio In/Out:	No	Yes
Ambient KB:	Yes	No, Yes§
Multitouch Trackpad:	3-Finger	4-Finger
SuperDrive:	Optional (External)	Standard (Internal)
Switchable Battery:	No	Yes
Size (Inches):	.16-.76 x 12.8 x 8.94	0.95 x 12.78 x 8.94
Weight:	3.0 lbs (1.36 kg)	4.5 lbs (2.04 kg)
Max Battery Life:	4.5 Hours§§	5 Hours§§
Intro Price Range:	US$1799, US$2499	US$1299, US$1599

* Both systems "borrow" main memory for video function. Minimum graphics memory usage is 256 MB.

** The MacBook Air "Core 2 Duo" 1.6 13" (NVIDIA/Late 2008) and MacBook Air "Core 2 Duo" 1.86 13" (NVIDIA/Late 2008) ship with a 120 GB hard drive and a 128 GB SSD, respectively.

† Apple officially supports a maximum of 4 GB of RAM but third-parties have been able to upgrade the system to 6 GB of RAM using one 2 GB and one 4 GB memory module.

†† An external 10/100Base-T Ethernet adapter is available for US$29, but due to the bandwidth limitations of USB 2.0, the MacBook Air cannot support Gigabit (10/100/1000Base-T) Ethernet.

§ The MacBook "Core 2 Duo" 2.4 13" (Unibody) has a backlit keyboard.

§§ Maximum battery life as reported by the manufacturer.

Ultimately, the MacBook "Unibody" models still are intended for use by a mass audience and the MacBook Air is intended for those interested in a premium, lightweight product. However, as the MacBook "Unibody" is decidedly more "premium" in its design and weighs less than its predecessor, and offers greater performance, connectivity, and expansion at a lower price point than the MacBook Air, no doubt some users who would have considered the MacBook Air when compared to the "White & Black" MacBook models will decide to buy a MacBook "Unibody" instead.

At the end of the day, those interested in buying a MacBook Air likely are frequent travelers to whom a pound and a half is more important than performance, connectivity, expansion, or price.

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Please refer to the Ultimate Mac Comparison feature to dynamically compare any MacBook Air model to any other G3 or later Mac.