I say evo, but I do own an iPhone. Im not really going to back it up versus an evo though.
I like the iPhone because im on tmobile. I get $10 unlimited data (no 3g). I also enjoy the perks of having the phone jailbroken. BUT I hate itunes and most of all I hate MACS.
I think Macs are alright...Not great, but something along the lines of alright. iTunes...I hate it as well. Actually, to be honest. I haven't really been syncing my 3gs through iTunes for about a year. (Excluding fw 4.0 update, and just a few days ago when I HAD to restore my phone which made it 4.2.1 and wiped EVERYTHING clean including SIM card).
As for the reception issue in the City....I agree. I usually go there quite often and always notice dropped signal strength. There's very few places here and there that I have absolutely NO signal. But for the most part I always have enough signal to make/receive calls, and actually use my phone. I do get A LOT of dropped calls, however it does seem SLIGHTLY less frequently now.
In the end...I say i4. I was actually deciding between BOTH of these phones. I always wanted to try out an Android phone, and I do like how useful iphones are for me. (actually using them for what I want/need). I actually may pick one up tomorrow since my battery on my 3gs is kind of messed up. At least once or twice a day it just shuts off (even with +/- 50% battery life left). I had to restore a few days ago since it went into an endless boot cycle.
I say i4...you'll be happy overall. ALTHOUGH....You DO have 30 days from when you buy the phone to return it/exchange it.