Looking at a new phone. My iPhone 3GS is getting sluggish (E.g. Settings takes nearly 10 seconds to load) and buggy as hell - I've had to wipe and reload it 3 times since the last update, because it keeps screwing up my audio books (Audible).

My Mozart is great and I'd stick with it as my primary phone, but Audible don't support it and the company Exchange Server certificate is invalid and, unlike Android and iOS, WP7 won't let you "ignore" invalid certificates. Invalid is invalid, basta! As I mainly listen to audiobooks or podcasts when I'm on the move, that counts WP7 out, until Audible decides WP7 is big enough to warrant supporting.

So that pretty much leaves me with Android as the choice of OS. I'm currently tossing up between the Samsung Galaxy SII, which my boss has just got and looks nice, but the build quality seems a bit "cheap", apart from the display, especially for the price, or the htc Sensation - it has a similar design to my Mozart and the Sense GUI is friendlier than the Samsung.

My only worry about the Sensation is the display, my Mozart has a couple of very large scratches, but the Sensation is supposed to have Gorilla Glass, so that should make it more durable.

Does anybody have any experience with the two devices and can give some feedback?

So far:

Samsug GSII:
+ SuperAMOLED display
+ bigger battery
+ faster
- build quality

htc Sensation
+ higher resolution display
+ Sense 3.0 GUI is "nicer" than Samsungs
- smaller battery
- a bit slower, but is that noticeable in daily use?

I wouldn't rate a GUI (launcher really) as there are 3rd party ones, the HTC skin and widgets are good though but my gf rarely uses them and there are alternatives

I have an original SGS and the screen is still immaculate after a year of use, if the HTC has gorillaglass I'd get that, but you can always root the phone (SGS, possibly not htc) to fiddle with the power/battery life

Went with the Sensation. Trying to set up my audio books and podcasts at the moment.

Android has improved a lot, since I last played with it. I still prefer WP7 in some ways, but until they sort out e-mail certificates and Audible support, I'll be sticking with Android.