Sony VAIO VGN-Z31VN/X in Laptops

The Sony VAIO Z-series is one of the smallest laptops we've ever seen, but it still tries to cram in everything you'd expect on a full-size notebook. Its 1.47kg weight is far less than most notebooks, and it's light enough to barely be noticeable when slung in a bag. The 33mm thickness is another reason why the Z-series is ideal for frequent travellers, as long as you've got a well-padded bag for added protection.

The VAIO's chassis should be able to withstand regular transport, too. The thin screen lid flexed easily but there was no sign of distortion on the Windows desktop when we prodded and twisted it. And the build quality elsewhere is beyond reproach - the wrist-rest didn't flex as much as we've seen in machines twice or three times the size.

Sony's now-familiar Scrabble-tile keyboard layout is excellent, proving just as comfortable as it did in the preceding Z-series, the VAIO Z21MN/B, and more comfortable than the scrabble-tile keys of the MacBook Air. The trackpad is decent, too: large enough to not prove restrictive, and with two responsive buttons.

The 13.3in screen, with its native resolution of 1,600 x 900, offers plenty of desktop space. The audio output is also surprisingly good for such a diminutive notebook, with the pair of small stereo speakers pumping out decent bass and a clear mid-range.

What's most impressive, however, is the sheer grunt this seemingly lightweight machine is able to deliver. It's equipped with a 2.66GHz Core 2 Duo P9600 instead of the low-power CPUs favoured by the MacBook Air, Lenovo X301 and Toshiba Portege R600, and the new part is also a step up from the 2.4GHz P8600 CPU included in the VAIO Z21MN/B. The result, unsurprisingly, is much more capable performance: the Z scored 1.45 in our benchmarks - twice as quick as all of its main rivals, and quicker than the 1.31 scored by the last VAIO.

And, thanks to dual graphics chips, this power doesn't come at the cost of battery life and portability. Using the Speed/ Stamina switch above the keyboard you can quickly swap between the Intel integrated graphics and the more powerful Nvidia GeForce 9300M GS chip; don't expect mind-blowing gaming, though: in our low-quality Crysis benchmark it achieved only 6fps.

In Speed mode the VAIO lasted just over two hours in our heavy use test and 7hrs 4mins in our light use benchmark. Flick over to the Stamina settings however, and you can turn this laptop from mobile powerhouse to indispensible business tool - we saw the VAIO last for a remarkable 9hrs 10mins in our light use test. The Nearest contenders, from Toshiba and Lenovo, last for six and a half hours: good, but not a patch on the Sony's all-day lifespan.

The VAIO's tiny frame manages to pack in plenty of decent components besides the CPU and pair of graphics chips. A 320GB hard disk is far larger than the 128GB SSD drives offered by Apple and Lenovo's rival ultraportables, but it's a trade-off between capacity and an SSD's speed and reliability. If you're not going to use all the space provided by the Sony, then an SSD model may be a better option in a machine that, inevitably, could take a few knocks.

The Sony matches the ThinkPad X301 for connectivity: both machines are kitted out with draft-n wireless, Bluetooth and an HSDPA modem, ensuring that it's possible to stay connected even without a wireless hotspot in sight, and a TPM module will be a welcome addition for business users.