I'm thinking about ditching my iPhone and going Android, so far the best contenders are the HTC Desire HD and the Samsung, which one has superior hardware specifications?
It really depends what you mean by superior. The Desire HD will be basically the same as the existing Desire but with a 4.3" screen and will have the same amount of internal storage as the Galaxy S.
The Desire HD will have 768 MB of RAM instead of 512 MB on the Galaxy S.
But the Desire HD will have the same Snapdragon processor as the old Desire, whereas the Galaxy S has the superior Hummingbird.
However, the Desire HD will have a 8 MP camera whereas the Galaxy S only has 5 MP, and the Desire HD has dual LED camera flash whereas some of the Galaxy S phones don't have a flash at all.
That sums up the major differences, and personally I'd lean toward the Desire HD, but you should compare for yourself and see what better fits your needs:
I chose the Desire HD over the Galaxy for a couple of fairly qualitative unscientific reasons.
On a more scientific level. As has been mentioned, while the Desire HD is still clocked at 1Ghz, it's snapdragon is the latest revision, made with the smaller process than the old Desire, and with the improved graphics. http://en.wikipedia.org/wiki/Snapdragon_%28processor%29
The screen on the desire is also bigger (and to my eyes awesome), but most reviews I've read say the colour and sharpness of the Galaxy is better. The Desire HD is also a big package overall, it may be a little too large for some pockets, I don't know how much more comact (if any) the galaxy is.