HTC Desire HD or wait til the new range of Android phones are announced in Q1 next year which will launch on 3.0 'gingerbread' version of Android.. which will be immense.
iPhone is too much money for nothing more than what the Android alternative offers, yet android generally offers more customization since its practically open source. iPhone does have more games yes but, Android is in its infancy in comparison, yet is growing faster.. so dont be suprised by the end of your 'to be' 24 month contract iPhones are
NOT the bee'z nee'z lol.
Battery life is improved a lot with v 2.2 of android [available on most/if not all networks now] for the Desire.
I'd reccomend the HD though due to its superior camera and larger internal memory capacity which is greatly welcomed if you plan on installing a large array of 'apps'. Screen is brutally awesome too if you plan on using it to watch video's from time to time.
Also, while im here - iPad is also an epic FAIL - there's a £250 10.1" tablet Android device out now with dual CPU, loads of RAM and 2.2 android - upgradeable to gingerbread 3.0 when its released. Fraction of the price yet more powerful - BOOM!
Steve Jobs GTFO