The marketplace gives consumers access to more than 300 products created using a 3-D printer.
The retailers topped Internet Explorer and Firefox consistency tests, respectively.
Dell.com had the best consistency score in Internet Explorer testing among large retailers measured in November, says Compuware Gomez. Last month, the computer maker and retailer had the most consistent Internet Explorer site loading time with a variation of 0.70 seconds. Apple.com had the best Firefox consistency score at 0.43 seconds.
Overstock.com (0.73 seconds) placed second in Internet Explorer tests. Apple.com (0.78) was third, followed by OfficeMax.com (0.84) and Costco.com (1.03).
In Firefox testing, Overstock.com came in second place behind Apple.com with a variation of 0.45 seconds. OfficeMax.com trailed in third place (0.64), with Dell.com (0.78) and Costco (0.93) rounding out the top five.
The average Internet Explorer consistency score among the 22 retailers measured in August was 1.81 seconds. The same group of retailers produced an average Firefox score of 2.30 seconds.
The consistency ratings take into account differences in the speed of web page delivery across multiple visits.
Click here for the full test results.