In fact, there really is little point in comparing the phones directly. The most obvious difference is price: the iPhone costs (99 plus 24 months of contracted tenure at maybe 0), for a minimum TCO of about 400, whereas the FreeRunner costs about 99 with no contract so you can use it on any of the very-economical pay-as-go plans that you have to look around for, say 0/month for a light user, for a total TCO of 40; so the TCO for this user would be about 3:1 in favor of Openmoko :-) (late note: my iPhone guesses are low; see this Yahoo Blog analysis for better figures). But that is not why people buy the iPhone or the Openmoko. People buy the iPhone for the glitz, for being cool, for being able to show off.
No, really. A week after the iPhone was released in the US and people were smuggling them into Canada, I was buying a coffee at a Starbucks in Toronto. Some dork dressed up as a Hollywood director left his shiny new iPhone right in the way where he knew anybody who wanted to get at the cream dispenser would either risk splattering on the iPhone, or have to move it. I very gently picked it up with the respect due such a device and moved it out of the way, whereupon he tried to launch into a tirade about how much he'd (over)paid for it. I wasn't in the mood to discuss it so I just said "if it's that valuable, keep it closer to you" and left (Seriously, I do have friends with iPhones, and they are reasonable people...).
Yes, really, the iPhone is sleek, and sexy. It is also almost completely a closed environment. People keep trying to open it up, because that's a challenge. People buy Openmoko not because it is sleek (the current hardware is, but the current software is not, yet; far from it) but because it is open. Open hardware. Open software. An open process company. The iPhone is a thing to give joy those who don't care how a thing works and have no care that they have paid 400 to surrender control of "their" device to Apple and to the carrier. The Openmoko Freerunner is a thing to give joy to those who love to tinker, who want to be able to (even if they never get around to) write their own applications in any of half a dozen programming languages. To make it do whatever they want, without regard for what the hardware supplier or the carrier wants. Openmoko.com encourages you do go "higher up and further in". Apple tries to prevent you. And that, I think, makes all the difference.