Right, grab a cup of coffee, soup, glass of coke or whisky, or whatever you prefer to do while reading a long text.
Let's get the most debatable thing out of the way first : the styling. Tastes may differ, but I find that in real life the HD looks like just another slab of glass with a metal edge. Too iPhone-like really.
The regular Desire has a more distinctive look, with it's slightly bent lower piece and the buttons. You really need to see them both in the flesh, as I wasn't too crazy about the old phone's styling when I saw it on the net. In real-life it looks stunning tho, and IMO it's even more stunning in silver.
There is a review of the HD next to the Z, in which you can clearly see that the HD's screen is pale in comparison to the Z. I posted it at the bottom of this post. The Z seems to have the same screen as the regular Desire (same resolution and size at least), so it stands to reason that the regular Desire has a better screen than the HD.
Secondly, depending on the size of your hands, the HD may be too big. The regular Desire is 60mm wide, which fits in my hand just perfectly. The HD's 68mm is a few mm too much for comfort in my case. It's doable, but I wouldn't want to have this massive thing as my main phone.
The HD may have a more energy-efficient CPU, but that's offset by the smaller battery capacity. Both phones should get you through the day just fine, but getting 2 days of use out of them will be difficult regardless of which one you choose. So you'll have to charge the phone every night anyway.
The HD has a lot more storage space for apps. To me that's a non-issue as I don't have many apps anyway. However if you prefer to have every gimmick and app on your phone, the HD will be the phone of choice for you. Sure, you can root the regular Desire and so on to create more space, but I'm doing a stock vs stock comparison here.
The HD lacks an optical trackpad, which can make navigation tricky when a lot of tiny links are closely together. Navigating the forum on a phone is difficult without it, as you'll be zooming in and out constantly in order to get the right link. So the regular Desire certainly has the edge there.
On the other hand the old phone has physical buttons which will probably wear out a lot sooner than those touchscreen-like affairs on the HD. I say "probably" because both phones aren't old enough to have any worn-out examples.
The HD has quickboot, which will catapult it from "off" to "ready" in just a few seconds. The regular Desire needs between 40 seconds and a minute to boot. Im not sure if that's really an advantage, but then again I only turn my phones off when they really aren't allowed to be on. That's not very often.
The HD also comes with htcsense.com, which allows you to do erase or block the phone from your PC, or send text messages via the PC (sent messages will also appear in your phone's outbox, so it's fully linked). The regular Desire may or may not get an upgrade to htcsense.com , but there is no definite answer on that. HTC apparently claim to be working on it, but I'm not holding my breath yet.
------
All in all, here's my personal input : If it were my $750, I'd get a regular Desire and spend the rest on a good camera. The 250$ should get you a camera that neither phone can get close to in terms of quality.
That being said, I'm selling a regular Desire and plan on buying a HD early next month. However in my case the HD would be a mere plaything, as my other regular Desire would remain my main phone.
I can't help it, I just love my "silver bullet".
The HD draws attention, and I'm not too sure I want that when I'm using it in public places. I prefer to have a lot of power under the hood, but I don't like the whole world to know about it. The regular Desire ticks all the right boxes for me. It's elegant, yet is one of the most powerful phones money can buy today.
To compare it with people : the HD is the huge hooligan which goes to bars looking for fights. Look at him and you know he's trouble. The regular Desire on the other hand is that quiet guy at that table in the corner, who wears a nice suit and minds his own business ... but is always ready to take that axe out of his suitcase and kill everyone.
