There has been much speculation regarding what processor Apple (NASDAQ:AAPL) will choose for its next-generation MacBook Air. Some expect the device to use Intel's (NASDAQ:INTC) low-power Core M processor aimed at ultra-thin laptops, two-in-ones, and premium tablets, while others think Apple will choose Intel's higher performance/power Core i3/i5/i7 chips.

It seems, though, that Apple rival Dell has spilled the beans on a key detail about the upcoming MacBook Air. According to a Dell representative quoted by Brooke Crothers in Forbes, the new Retina MacBook Air will feature the Core M processor, not the "full" Core i5/i7 parts.

Trading performance for form factor
The Intel Core M processor, to my knowledge, uses the exact same silicon die as the 15-watt Core i3/i5/i7 chips with the lower graphics configuration (known as GT2; the higher-end configuration is GT3). The difference is that the die is attached to a slimmer chip package that reduces its footprint. The chip also runs at lower performance levels in order to "fit" into a smaller power envelope.

I believe a 12-inch Retina MacBook Air using a Core M processor is likely to offer lower performance than the Haswell processors found inside today's 11-inch and 13-inch MacBook Air models. However, if Apple does a good job with the industrial design of the system, the chip might be able to run at higher speeds for longer, avoiding the seemingly embarrassing performance issues experienced by the Core M inside the Lenovo Yoga 3 Pro.

Looks like a very slim machine
A number of photos of the purported Retina MacBook Air have hit the Web, and the machine appears very slim. While some users might not like what could be a performance regression, users who value portability could be quite happy with the system

I suspect this will make Apple's MacBook Pro line of laptops even more attractive to more performance-hungry users as the performance gap between the Air and the Pro lines should widen.

But is it too slim?
In the Forbes article, Donnie Oliphant, Dell director of XPS product marketing asserted that at some point, when a laptop is made too thin, battery life and performance will be compromised. Given that "all-day battery life" was a key selling point for the MacBook Air launched in mid-2013, though, I don't think Apple would see a regression there.

That would be detrimental to the user experience, and Apple is well known for making smart, user-experience focused trade-offs.

What I remain concerned about -- if Oliphant is correct that the new Retina MacBook Air will feature a Core M -- is performance. I expect performance as measured by a suite of popular benchmarks to regress from the old MacBook Air models to the new Retina MacBook Air, but I'm more interested in the subjective impressions from reviewers.

Will the new MacBook Air, even if it powered by a Core M, feel snappy? Will the common programs people ran on the old Air run well on the new Air? If the reviewers report that the machine feels fast, then going with Core M and the slimmer form factor would arguably have been the right decision. However, Yoga 3 Pro-like performance issues could be a showstopper.