A benchmark test for rich internet application (RIA) frameworks claims Apple’s OS X lags Microsoft’s Windows XP on Intel when rendering HTML, being just over half as fast.

Sean Christmann, an experience architect at user interface specialist EffectiveUI, released the GUIMark benchmark following concerns over the lack of a proper test to compare RIA frameworks and technologies such as Adobe Systems’ Flex and Flash, Java’s Swing, Microsoft’s Silverlight and good, old HTML.

EffectiveUI specializes in building RIAs and numbers eBay, Ford, Discovery Channel and United Airlines among its clients.

Christmann, an experienced user interface designer who led the development team for eBay’s Desktop, tested a range of RIA frameworks on an Intel-based MacBook Pro under Windows XP and Mac OS X 10.5 and found that XP consistently outperformed OS X.