Please do follow my articles (all cross-posted to the General forum here), I've published some real benchmark data on this q some weeks ago.
In a nutshell, in WM5 AKU2 (which also means AKU3 / Crossbow), PIE has been greatly enahced and is, now, pretty similar to that of Opera Mobile, teh, up to now, fastest full-fledged browser.
The upcoming NetFront 3.4 is also very fast (as opposed to version 3.3 used in full browsing mode)
Microsoft MVP - Mobile Devices
, 2006, 2007, 2008. Make sure you follow my PPC & SP Mag Expert blog HERE