kiwijunglist: Desire HD (from what I've read)
+ Made by HTC
+ Better camera
+ Larger screen 4.3"
- Too large for some pockets?
- Currently sold out
Galaxy S (from my experience)
+ Amyloid screen
+ Fits better in pocket
+ Faster GPU
+ Better external speaker / ?better audio?
- Crappy software support from samsung
- Comes with kies
- GPS is a little dodgey
- Camera is a bit crappy
- Lags a lot unless you install lagfix
If you don't mind the large size I would pick the Desire HD over the Galaxy S.
No issues with my camera on my SGS