They are available on multiple carriers (iPhone will lose the battle based purely on availability unless they open up to other carriers)
The amount on restrictions, or lack there of, on developing applications
Competition – Multiple phones [...]

BJ sent me a link to PhoneGap yesterday and asked me to take a peek at it, here are my two cents on it.
PhoneGap as a whole is extremely impressive, but it’s probably more ambitious than functional at this point. The main selling point for the platform is that there is practically no barrier [...]