People feel strongly about this but...
I have a iPhone 3GS through work and bought a iPad 3 simply because the screen looked awesome , i dont have a laptop and wanted something that didn't require me to power up my beast of a pc to check a web page ( work don't like us using their devices on non work related stuff) . Bottom line is:
iPad gets warm, not hot, after 30 mins on a game or hd movie but never a problem or uncomfortable.
Iphone 3Gs seems to have a similar wifi range and speed over same distance. This is using a "n" router but the 3GS doesn't have n capability so one would expect the iPad to be far superior. Sorry folks - it ain't.