Tough HTC/Network Decision

Orange rang me up a couple of weeks ago and informed me that I'm due an upgrade.
I've been a Blackberry fan for the last two years, but their lack of development and poor reviews have led me away from getting the Torch.

So I had a look around at reviews and decided to make the jump to HTC, I'm a tech freak so it should suit me nicely.
I was then stuck between the two new Desire's (Z and HD.)

Since I'm now fully adapted to using a keyboard, the Desire Z was my immediate choice.
I then looked at reviews and was extremely stuck between the two.
I phoned Orange and they only sold the HD so they offered me that.
Now, two weeks later, they still haven't got any in stock.
Sadly just another thing to add to the list of problems I've had with them in my two years there!

So now I've decided to go against Orange, and opt for a new provider.
I've been told that Orange add loads of bloatware onto Android's? Is there any providers that don't do this? I can't afford to buy one outright so contract is my only option sadly.


So, my questions are:
a) Has anyone who has used both the Desire HD and Z got any strong pros/cons for either phone? The keyboard is obviously better and I'm reading about better battery life on the Z too.
Z seems to get worse reviews in most places though but nothing to really back up negative reviews apart from tiny niggles.

b) Which provider offer the best support and are generally a much more pleasant experience than Orange and don't cram the phone with bloatware?

Any responses greatly appreciated, thanks in advance!