A few months back when i was still deciding what to get between these two cameras i read a lot, but when the time comes for me to buy i made a huge mistake (buying without ever handholding either one of these models).
i chose the 500D because its cheaper by $400 and i have a canon service center near me, 3 years warranty and crumpler strap. While the nikon D90 only has a 1year warranty from the Nikon Authorized distributor here in our country which is a few islands away...
then suddenly after a few weeks of excitement, i had a buyers remorse, i keep think what if i bought the nikon d90, they all say its better ergonomics wise, feature wise etc etc... so yesterday, i had a chance to buy 1 for my brother, i was expecting to get blown away by it, i tested it for a few hours checked its features, settings and buttons and came to the conclusion that i did made a good decision a few months back.
except for the shutter sound, grip and uhhhmmm what else? ahhh nothing else. i just did not like the layout and suddenly appreciated my 500D more.