G1. It is the only phone with a hard keyboard. When the keyboard is opened up you will get several events/activity relaunches that will not happen on the touch screen only phones. If you are doing apps it really doesn't matter if you get the dev version or retail one.
Going forward, you are probably going to need to get several phones as the hardware diverges. For example the samsung has a 5way instead of a trackball. Depending on how you are using the trackball, that could be a significant difference.
But as far as looks, get the samsung. It is by far the best looking android phone that I have seen so far.