On the face of it, the Sony TZ17 and the Toshiba Portégé R500 have plenty in common. They weigh practically the same, have similar-sized screens, and share ridiculously tiny dimensions. Both use Intel’s ultra-low voltage range of Core 2 Duos and both will happily fit into the very smallest of shoulder bags.

Yet while the Sony costs $3599, the Toshiba weighs in at nearly $600 less. If you think that means there’s no reason to be tempted by the more expensive Sony, though, think again – the R500’s build quality is noticeably less impressive than that of the TZ17. In particular, the Portégé’s chassis has a plasticy feel, with a little too much flex in the palmrest for our comfort. As such, the R500 is just that little less reassuring when the time comes to stuffing it in a bag or running for that train.

The different scale of budget shows through when it comes to usability, too: the keyboard in particular feels noticeably spongy. That said, the keys themselves are bigger leading to more accurate typing. The big on-paper advantage the R500 holds over the TZ12 is the screen, for Toshiba has designed this Portégé to be used outside. It achieves this through transflective technology, and it definitely works: even in bright sunlight, we could see the screen’s contents without any sort of strain. The 12.1in diagonal and 1280 x 800 widescreen resolution is fine for office work, and we’re also pleased that Toshiba has resisted a showroom-friendly glossy finish.

The transflective screen does have some weaknesses though. Horizontal viewing angles are poor, with a difference in contrast noticeable even when you view the screen from dead-on. Vertical viewing angles are no better, and the backlighting on our sample was noticeably uneven, with obvious amounts of light leaking from the top and bottom of the screen.

Another drawback of the R500 becomes noticeable when you pop it on your lap for a spot of work. Even when simply running Microsoft Word, the R500 gets uncomfortably hot. Toshiba wards off lawsuits from workers with burnt knees by including a warning sticker on the bottom, but the amount of heat is very unwelcome. The Sony TZ17 includes exactly the same processor, but has nowhere near the same amount of trouble dissipating the heat. Part of the reason for this heat build up is the R500’s largely passive cooling – even when working hard it remains virtually silent.

The processor in question is Intel’s Core 2 Duo U7600, running at 1.2GHz. 1GB of RAM is included, and although the R500’s final application benchmark result is an underwhelming 0.56, we never had that wading-through-treacle feeling when browsing the internet or working on documents. Start photo editing with a couple of applications open, though, and it’s a different story.

On the plus side, battery life improves as a result of the ultra-low power processor and a lack of battery-draining fans. In light use, we saw an excellent 6hrs 19mins. Intensive use saw the system’s single fan kick in, and the amount of time it could survive away from the socket fell to 2hrs 23mins. Both times are impressive, but they’re still almost an hour behind the TZ17.

One area where the R500 has an advantage over the TZ17 is storage: a 120GB hard disk is supplied (though you can also buy it with a 64GB solid-state hard disk, for an extra $750). But we didn’t like how easy it was to set off the R500’s protective hard disk sensor at default settings. Like Sony, Toshiba has managed to fit an optical drive into its tiny machine, with the drive capable of writing to all kinds of disc including DVD-RAM.

Taken on its own merits, the R500 is still a good ultraportable: it’s impressively small and light, and if every gram counts, it’s well worth considering over more expensive options such as the TZ17. But it isn’t without its failings, and if you can afford the TZ17, and working outside isn’t a priority, then go for one of them. Alternatively, there’s the slightly larger Sony G11 (see A-List), which costs more but doesn’t suffer from the R500’s heat problem, besides offering an incredible nine hours of battery life.

However, the R500 is temptingly decent value for money, and if the idea of working in the garden or next to a sunny window appeals, there’s nothing else to match it.