This is a difficult one. Comparing Android apps to iPhone apps it depends on the functions it benefits from, for example, a few superior Android apps IMO:
Last.fm/spotify/Pandrora - All superior on Android due to multitasking. Running these apps on an iPhone leaves you with no ability to use any other functions whilst it is open. No browsing and streaming, no realtime scrobbling of what music you're playing. No quickly answering that SMS you just received without closing the app and replying. Hopefully the next update will give some kind of multitasking to alleviate this issue
AndFTP - As Android has full access to the SD card filesystem, you can upload and download files at will to any FTP source. I have ANDftp installed on my Hero and can upload or download pictures, music, video and documents at will to my iMac as I have it set up with FTP access.
Gensoid/NESoid/SNESoid (
et al) Emulators - Apple just wouldn't allow you to use Emulators with unauthorized roms so naturally, classic machine Emulation is better on Android and with the hardware in the Droid/Nexus One, the older generation of consoles will perform better than they ever have. Jailbreaking solves the emulator problem but there is a lot of negativity (especially on these forums) about jailbroken iPhones.
Things that are better on the iPhone? Stuff that doesn't need multitasking to function better and games. As Android hasn't supported 3d hardware acceleration as well as Android 2.1 does now, the games have been lacking.
What the iPhone does, it does well and if you are as happy as you seem to bewith your 3GS, why bother switching? You also have issues with Google so not bothering with Android is a no-brainer IMO.
I moved away from iPhone OS as I do multitask on my devices (streaming music + browsing) and have been doing so since my first Symbian smartphone, many moons ago.
We haven't fully seen what the Nexus One is capable of yet so I'm looking forward to getting one and seeing where it goes.