The entry level MacBook Air used to offer the same 1.4GHz processor but it was updated in 2015 to a newer 1.6GHz processor and saw a slight speed bump thanks to that. The MacBook Air also benefits from an SSD, or Flash drive, which is faster than the standard hard drive featured in the 21.5in iMac desktops, the entry-level 27in 5K iMac, the entry-level and mid-range Mac mini and the standard 13in MacBook Pro.
There's not a big difference between the specs of the 11in and 13in MacBook Pro models, the only real difference there is the storage and screen size.
If you are considering the difference between the 13in MacBook Pro Retina and 13in MacBook Air the differences are slightly more pronounced, but the price isn't hugely different. The entry-level 13in MacBook Pro with Retina display costs £899 while the 13in MacBook Air with less (flash based) storage costs £849. the Retina model not only has a better screen, it also has a better processor and more storage.
The 13-inch MacBook Pro with Retina Display starts with a 2.7GHz dual-core CPU at £999, which is comparable to the 2.8GHz 21.5in iMac, which costs £50 more at £1.049. The laptop does offer flash storage as standard, though, which will make it faster. And this iMac doesn't have a Retina display (although it does have a bigger display).
It's also comparable to the 2.6GHz Mac mini which costs just £569 - as you can see, you don't necessarily have to pay more to get a higher spec machine.
The 15-inch MacBook Pro with Retina Display has a more powerful 2.2GHz quad-core Intel Core i7 processor, it costs £1,599. That's the same price as the 3.2GHz iMac with Retina 5K Display.
Then there's the Mac Pro starts with an even more powerful 3.7GHz Quad-Core Intel Xeon E5, that costs £2,499, which isn't a lot more than the top of the range 3.3GHz iMac at £1,849.
Although, as you can see, there are areas of crossover between the MacBook Pro, MacBook Air, iMac and Mac mini, it's clear that you get a lot more processor bang for your buck on the desktop range. This isn't just a number on a spec sheet: the faster speed will make a lot of difference if you're using Photoshop and 3D imaging software or video editing. It also extends the lifespan of the machine, ensuring it'll be able to run newer software for longer. However, the desktop machines can be let down by the slower hard drives, if you can opt for the build to order fusion drives in them (fusion drives combine a flash and hard drive for the best of both worlds) we recommend you do.
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