Weight:
G1 = 158g
iPhone = 133g

Battery life:
G1 = 5 hours talk time, 130 hours standby
iPhone = 5 hours talk time, 300 hours standby

Screen size:
G1 = 3.2in
iPhone = 3.5in

Camera:
G1 = 3-megapixel
iPhone = 2-megapixel

Capacity:
G1 = 2GB, expandable to 8GB
iPhone = 8GB or 16GB

Key features:
G1 = touchscreen, Qwerty keyboard, internet access via 3G and Wi-Fi, additional downloadable content, one-click access to Google search services, built-in GPS and compass for easy navigation, push Google email, instant messaging.
iPhone = touchscreen, virtual keyboard, multi-touch gesture support, web access via 3G and Wi-Fi, additonal downloadable applications, GPS and Google Maps, push-email, full web browsing.

Extra applications:
G1 = extra software downloadable from Android Market. Includes games, such as Pac-Man, and useful software, such as Shop Savvy, which allows users to take photographs of a product barcode, send it to Google, and then retrieve price comparison results.
iPhone = extra programs and software downloadable from Apple App Store, including games such as Super Monkey Ball, and other applications, such as language dictionaries, travel guides, restaurant recommendations.

Entertainment:
G1 = one-touch music downloads from Amazon MP3 store, 2GB integrated storage, expandable to 8GB.
iPhone = one-touch music downloads from iTunes music store, choose from 8GB or 16GB storage.
Source: www.telegraph.co.uk