I have both the G1 and the iPhone 3G and it would be a tough call to only pick one. Right now the android platform is new, and just like the iPhone when it first came out, people will complain all day long. The G1 has that more "customizable" feel, but the iPhone has over 4,000 apps avaiable. If your in a 3G area I say go for the G1, if you want better media than go with the iPhone.
I will be doing a G1 vs iPhone post on my blog soon, its the link in my sig, so keep an eye out. I'll have pics and the whole 9.
Here is a link to my iPhone vs G1 review. Its pretty extensive so get ready for some reading:
Apple iPhone vs T-Mobile G1
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