It's good that Remmy provided another take on it, but I'm concerned about the factual content of some of its. I definitely agree that the iPhone wins in terms of ease of use (but that's always a double-edged sword that comes with reduced flexibility) and camera quality (including the FFC). I'd add that the iPhone4 has better battery life out of the box, although of course you can have multiple batteries, or a larger aftermarket one on the DX.
His comment on hardware is unfathomable, as it's simply not true (the iPhone4 does not have more RAM - both phones have 512mb, and it's CPU is underclocked below 1ghz...several testers, including Anandtech have shown this).
The main difference is actually in the OS, as the iPhone4 makes better use of its GPU by having more of the UI offloaded to it - this is why so many of the transitions are extremely smooth, even when the device itself slows down. It's also why iOS is so limited in terms of UI customization. Gingerbread actually adds quite a bit more GPU acceleration to UI functions, and I can tell you that running the DX on Gingerbread is a thing of beauty. In fact, running LPP over the new Gingerblur is very nice, and I enjoy it far more than any iOS device, although that's my subjective opinion.
As for iOS apps being "more polished"; they all look more alike, and part of the UI variety on Android apps does lead to some of them looking more amateurish, but then I can also wirelessly sync all of my media right now (even before Music Beta) through an Android app, while iPhone users have to hope that Sir Jobs deigns to give them the ability to cut the cord. So again one users "polish" is another ones "shackles".
The DX2 will be every bit a competitor to the iPhone4gs, which will have almost no new features aside from playing more complex games and probably a better camera. And the new Blur on Gingerbread isn't bad at all (I just can't give up my LPP widgets and task bar). But Gingerblur is fast and stable, and nothing to be ashamed of.
So again I'd urge the OP to think about what is wanted in a phone and to try them both out. Sometimes you are surprised - I used to think the iPhone4 had a better build quality (it sure looks fancy in the photos) but in practice I hate it, as the feel of plastic is simply not comfortable to me (and I always feel like I'm going to break it). I also prefer the industrialized look to the "fine art" of the iPhone. But of course others love the look and feel of it, and again that's all personal opinion.