A lot of people seems to be comparing the two phones by "Speed" "Responsivnes" and "Performance".
Now my friend got an Evo 4G, and I an HD2, and I must admit, I'm afraid that the EVO is better on those terms. Yes, it is a bit bigger and bulkier, but Android does run better on it whatever people says. When browsing the home screens on Android on both mine and his phone, it is clear that the Evo 4G is faster. The benchmarks may say something else, but when it comes to what really matters, which is the user interface, and how it works, I must declare the Evo the winner. Its jut a lot faster, this might be hard to understand, but trust me, when sitting with both devies in your hands, there's no doubt.
Also, when it comes to hardware, the screen itself, feels a bit more responsive on the Evo, but nearly as fast as the Iphone, or Xperia X10 mini.
But which phone is the winner? For me its the HD2. Not because of the way that it runs Android, or because that's its a bit smaller. But because of the community that it has created. Never before have I seen so many people dedicated to develope, test, and take part in all kinds of porting and hacking. It is beatifull to see Android work so good on the phone even tho its miles away from being perfect.
It is stunning to see the hundreds if not thousands of ROM's developed for this one and only phone, where people has been so great at providing feedback, to the skilled developers that this community boosts.
And that's why that this phone wins. Because of you! You guys are all the best