Unanswered: HTC or Samsung?

Hi,
I have an HTC Desire, but want to buy my brother a new smartphone for Christmas.
He has an ipod touch, so gets the ipod apps, so thought with a phone with Android, he has the best of both worlds.

So...
would anyone out there recommend getting the HTC Desire HD, or the Samsung Galaxy S, or ......
would the Windows 7 phone be better?

Any experiences would be appreciated please

Thankyou.