I haven't touched the Desire, so I can only write about the Legend.
In my own opinion:
The Legend looks GREAT, ATTRACTIVE & CLEAN design, & feels SOLID. I get so much compliments about the phone, even old folks, who don't care about phones, think the my phone is very nice looking.
However, the sharp edge on top of the earpiece sometimes hurts my ear.
It performs very well & smooth.
I use the phone MAINLY for calls & text messages. & I don't play & care for games on the phone. Therefore, the Legend's SIZE is PERFECT for me.
The phone has GREAT audio quality, which is nice & clear, & has good battery life.
I read somewhere that says because of the Legend's aluminum case, it doesn't get excellent signal. However, the reception has not let me down yet.
I'm also using HTC Touch Diamond 2, & HTC HD. My house has really bad signal & I have NO PROBLEMS with the Legend, whereas the other 2 get drop calls constantly.
It has 4 plastic buttons that feel REALLY CHEAP. You'll be disappointed with these buttons.
It has some other Cons, but you'll get that with the Desire too, so I won't go there.
I think you should also go to the Desire's board & ask what they like & dislike about the Desire & then make your own decision.
For now, I'm keeping the Legend until I can find a phone suitable for my need.