Amazon.com and Dell came out on top in Keynote Systems’ rankings of online computer hardware retailers for consistently providing a solid shopping experience.

To compile its rankings, Keynote studied the online experience of 2,000 customers as they shopped on 10 sites that sell computer hardware: Amazon.com, Apple, Best Buy, Comp USA, Dell, Gateway, HP, Lenovo, PC Connection and Sony.

Keynote measured the sites according to 250 customer experience-related metrics and 40 performance metrics. On the customer experience front, Keynote used a combination of Web analytics and traditional market research to evaluate such categories as satisfaction with the online purchasing process and customer support, as well as a site’s overall design and organization.

While Amazon.com and Dell stood out in those areas, two different retailers nailed the performance evaluations. Sony took top honors for site reliability; its site experienced little or no downtime during the monthlong evaluation period, Keynote says. Comp USA placed first in terms of site responsiveness, which Keynote ranked by measuring such metrics as how quickly pages loaded and transactions completed.

Uptime was a challenge for a number of computer hardware sites during the evaluation period. Keynote says several of the sites recorded major outages that left them unavailable to visitors for more than 40 hours during the evaluation period, but it declined to identify those retailers by name. The average across the computer hardware industry for site outages is two hours in a 30-day period, Keynote says.

Many computer hardware sites also recorded slower than average broadband performance because of the increasingly complex pages offered up to consumers, Keynote says.