When Microsoft demoed Windows Phone 7 Mango for the first time in May it made a big deal of telling anybody who would listen that its IE9 browser was the fastest browser on the block thanks in part to the built-in hardware acceleration.

Pocket-lint was one of those who did listen and we put our dev unit from Microsoft running Windows Phone 7 Mango up against an iPhone 4 running iOS 5 (first beta) to see how true Microsoft's claims were.

Not very, we found - over a series of 20 side-by-side tests the Windows Phone 7 lost out on frames per second to the Apple iOS 5 every time with the average for the Mango device being 22 fps against 27fps for the iPhone running iOS 5.

However, in Microsoft's latest demo - it claims to blow iOS beta 3 out of the water, running the fish HTML5 app at 50fps, against just 14fps for the iPhone 4 with the latest build.

Time for another Pocket-lint investigation we think.......stay tuned.