It really depends on what he's looking to do with a bb. If it's strictly to stay connected and receive/respond to email and do some occasion web browsing, then the 8700 will be great. Plus it has a great screen and full QWERTY keyboard.
If he's into multimedia (pics, videos, MP3s), then the 8100 should suit him. It's smaller and more like a phone, although the 8700 is a great phone as well.
Your Neighborhood PR Guy
Blackberry 8703e (Verizon)
"There's a time for compromise...it's called later".