I have both the N1 and iphone 4 (on AT&T) and love them both. They're like children or pets, each has strengths and weaknesses, and each does cool things that surprise me all the time.
The N1 is awesome (I think compared to other Android phones) because Google updates the Android OS pretty fast, and it "should" make the cut for Gingerbread at the end of the year. Plus as an HTC phone I can learn/hack a lot at XDA Devs. I wouldn't want an Android w/o their (XDA's) support so I'll stick with HTC models for now.
The iPhone is cool because - well I'm posting on MacRumors so I don't need to tell you guys why it's cool.
I agree about battery life, in my usage patterns, the iP4 "feels" like it lasts about twice as long. But that may be because of how I use both of them. Either way the iP4 battery life is great for me coming from the 3GS.
One funny point: The N1 can be "rooted" w/o any special tools, just boot into the bootloader and you can flip the switch. You are warned you'll lose your 1 year warranty if you do this however. But because I can really do everything I'd want (change keyboards, launcher shells, wifi hotspot, etc.) w/o rooting, I'm actually completely stock from a "hacking perspective" on this phone for longer (about 4 months) than I've been with any phone for a while.
The iP4 on the other hand is about 75% of what I want when not Jailbroken. I really miss things like SB Settings, MyWi, Lockinfo screen, notification management, and (IMHO) much better multi-tasking that I can control.
So the the one with the keys built-in I'm leaving locked, the one that comes locked up tight I'm left waiting for the keys. Ain't it always the way?
Both are fun to have and I feel like I have the top (or damn close) of both OS ecosystems represented here.
That is until WP7 comes out.