Had I been in your position, I wouldn't have gone for DHD (For me, 4-4.1" is the max, 4.3" is a bit too big, for one handed operation). If you find hardware keyboard useful, wait for HTC Desire Z. (For me, it just adds to the weight, I'd ideally like Desire HD similar phone ,3.7" inch , good screen and camera..but right now you'll have to make some compromises)..
If you are willing to play around with your device, SGS is a very good option. (Esp. because of Nexus S

).. Else, if you are unwilling to root/customise, HTC phones would be better. And now that prices have gone down for HTC Desire, it is quite a good choice, I guess..
BTW, any major reason why you're not considering Nexus S? (Lack of gorilla glass, 480p video recording, no external sdc card support being the major minuses, I believe??) Other than the minuses, it is Galaxy S minus the Samsung's customisations with the assurance of latest OS updates as soon as it is released..