right I have extensively researched and studied specifications of both phones.
Good points going for the Galaxy are : Better screen, 4 times faster graphics, better battery
Good points for the Desire : More Ram, Better processor(about 5%) but it has now just received the frodo 2.2 update, which has increased processing speed by 30% and the os is a million times better
If you want a serious phone then go for the desire, If you want a toy to mess around with go with the samsung.
I have both the htc desire and the galaxy s.
id reccomend the desire for people moving across from the iphone as its great straight out of the box and has lots of nice widgets pre installed. The galaxy s, despite being better in hardware, requires a little tinkering and setting up and customising to get the best out of it before it whups the desire's ass, and as such would reccomend it for those coming from windows mobile as they will find the minor setting up a breeze.
Galazy S if I had to get one.
Haven't been a fun of Sammy's UI, so won't get neither, but I'm looking forward to Desire HD, and whatever Samsung has to better that.