Acer is the latest company to jump on the ultra-portable bandwagon with Aspire one, a 2.2-pound unit that sports a near-full size keyboard and can yield as much as six hours of battery life per charge, according to claims by the PC maker. Rival Asus last month began shipping the Eee PC 900, an enhanced version of the mighty little unit it introduced late last year.

Specs of the Aspire one read much like those of its rival Eee. Both units are built around an 8.9-inch backlit LCD with 1024 x 600 maximum resolution and both include a Web cam. The Aspire one is nearly an inch longer and about a quarter-inch wider—essentially a draw on overall dimensions. Asus includes 1GB DDR2 RAM but only 4GB NAND for non-volatile storage. That’s compared with Acer’s 512KB standard (expandable to 1GB) and 8GB NAND. In the Linux version of the Eee, Asus throws in 16GB more NAND for a total of 20GB. Not too shabby. Both have WiFi

Acer adds niceties like a five-in-one card reader (SD, MMC, Memory Stick, Memory Stick Pro and xD), software that merges storage from that port to its second SD slot, an 80 GB magnetic hard disk option and a keyboard it says is 95 percent of standard size. Asus counters with three USB 2.0 ports and an external VGA port.

Now to the processor. Asus delivers its unit with an Intel Celeron M. And while Celeron’s never been my favorite, I don’t recall ever hearing that the circuit is in short supply. Not so with the Aspire’s processor: The Intel Atom, for which availability has been spotty.

Both units are available with Linux or Windows XP. The Eee PC 900 lists for US$549 but is available in most outlets I’ve seen for around $399. The Aspire one lists for $379 and is scheduled to begin shipping in July in sapphire blue and seashell white, reportedly with more colors coming later this year.