i have been finding Tons of different "pan =# of serving charts", and have a hard time deciding which one to go by. some of them are sooo different! does anyone have any suggestions as to what charts they use to determine number of servings... thanks

I go by the Wilton serving charts. They have serving sizes for both party and weddings. The most important thing to do is to choose a chart, and stick with it!
http://www.wilton.com/cakes/making-cakes/baking-party-cake-2-inch-pans.cfm
http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm

Every caterer cuts to the Wilton Wedding chart You can provide more cake assuming larger slices, but you'll just be giving away free cake. Really, this is something Wilton really got right.