With the MacBook Air, it’s clear Steve Jobs and his marketing friends were focused on one end-line – “the world’s thinnest laptop” – and they achieved it in style. Lenovo, by contrast, is ruled by its engineers. And although the firm is using the tagline, “World’s thinnest and lightest 13.3in-wide laptop”, that’s never going to grab front-page headlines.

Having used both laptops in anger, we know which one we’d buy – and you’re not going to see it featuring in many TV campaigns. That’s partly because the X300 is no oil painting. It follows the traditional all-black ThinkPad design and, if you were feeling cruel, you could even accuse it of being boxy. One thing it does share with the MacBook Air, though, is excellent build quality: grab this laptop by the corner and there won’t be the slightest bit of flex.

You’ll also be surprised by how light it is. With the three-cell battery in place, the ThinkPad weighs 1.45kg – that’s just 70g more than the Air. And the X300 has the advantage of a built-in DVD writer. But where the ThinkPad really moves ahead – and the reason we’ve come to regard it as a new form of laptop – is its 13.3in screen and full-sized keyboard.

These two factors make it very usable as a main system. The X300’s keyboard is an absolute pleasure to use – not only because of the keys’ size, but also their distinct travel. The screen, meanwhile, benefits from a 1440 x 900 resolution, which is a notable step up from the 1024 x 768 of a typical 12.1in display. The panel itself is brightly lit and boasts good contrast, but it isn’t perfect. Its colour reproduction falls short of the very best panels, and you have to position the screen at an angle of around 110 degrees to get the perfect image. This didn’t bother us in general use, though.

Another reason we’d be happy to use the X300 as our main computer is its speed. A score of 0.68 in our benchmarks is roughly half that of the very fastest laptops, but there’s no task it struggles with. Sure, it won’t process a video as fast as a Penryn-based system, but few people need that level of speed. Our test sample also benefited from a solid-state disk rather than a traditional hard disk, reducing the stuttering effect that sometimes plagues ultraportables. Mechanical disks will follow, but at launch Lenovo is only releasing a solid-state version of the X300.

This has an inevitable impact on price, and it also reduces the amount of storage available. Rather than a 200GB disk, say, you’re limited to 64GB. And once Windows has had its way, and Lenovo has siphoned off a partition for its recovery software, you’re left with a mean-looking 40GB.

Theoretically, the solid-state disk should also lead to greater battery life, and with the three-cell battery in place the X300 lasted for a highly respectable 3hrs 58mins. In our intense-use test, that dropped to 2hrs 8mins, so you can expect something in between depending on your usage. If you want more life, you’ll need to use the six-cell battery, and this will come as standard with the X300. We didn’t have a sample to test, but it could push the ThinkPad to the eight-hour mark, with the sacrifice being an extra few millimetres in height and a couple of hundred grams in weight. Another option is to replace the optical drive with a slot-in three-cell battery.

Lenovo does make a couple of sacrifices with the X300: there’s no docking station, although the USB port replicator does sport a VGA output that supports screens up to 1280 x 1024. It’s also a shame the bezel is so large around the X300’s panel, contributing to a slightly retro feel. Plus, there’s no dial-up modem (although you can buy an external USB modem from Lenovo).

But there are a huge number of compensations: a light to illuminate the keyboard in dark conditions; a superb array of rescue and recovery options, including a full emergency OS you can boot into if all else fails; an internal 3G modem with support for HSDPA; three USB ports compared with the MacBook Air’s one; and speakers you can actually hear music on.

The drawback for the X300 is that price, but we fully expect retailers to shave a significant amount off this figure. More importantly, the Serial ATA disk versions will cost much less. If you don’t need the benefits of solid-state technology, wait for the new models. But if you’re after the last word in reliability, usability, quality and portability, your money won’t be wasted.