TPF has plenty of working pins for sale, but limited project pins and used parts selection at the Saturday parking lot. MANY vendors selling their new parts/mods. Nice convention center. Great show and I go every year.
Allentown/Pinfest - 300 pins on freeplay, many vendors (but not as many as TPF), many project pins and lots of used parts for sale. This more of a swap meet feel.
Chicago Expo - Haven't been before but I'll try to make it this year.
SFGE - 250 pins and arcades on free play, seminars, in a hotel convention hall. Many of the pins will be for sale. NO project pins or used parts dealers/swap meet.