- 电话呼叫的接待 - 在美国可能很好，但Au？ 呢？
- 数据速度 - 是3g和/或hsdpa可用？
- 手机速度 - 规格是相似的，但它实际执行哪一个，它将在澳大利亚境内表演？
I've done some research and there seem to be advantages and disadvantages to each. I'm fairly confident that I can physically run both in Australia, however which will give me the best experience given the mobile bands and technology available here?
The main things I'm concerned with:
My recommendation would be for you to get the Nexus One. Though the Nexus One and the Desire both have the same 1Ghz Snapdragon processor, the Nexus One now runs Android 2.2 "Froyo" that has a JIT compiler that can execute code up to 6x as fast as the Android 2.1 on the Desire. The fact that the Nexus One is the official Google phone means that it's going to be the first to receive the latest software, while other devices (like the Desire) will lag behind or not get updated at all.
The other big deciding factor is HTC's Sense. Though many people like Sense, there are others, including myself, that prefer the stock Android UI. If you can, try and see if you can play with both UIs before deciding which one you want to buy (stock Android 2.1, which can be found on the Motorola Milestone, is similar to stock 2.2, but lacks a shortcut to the phone dialer at the bottom on the home screen).
This doesn't directly address your three main things, so downvote me if you must, but one big current advantage to the Nexus One is that it's really the Google phone and gets preferential treatment when it comes to Android updates.
In the US at least, carriers who release and subsidize phones often call the shots as to what software ships on the phone and when it gets OS updates, if ever. The N1, being unlocked and carrier neutral doesn't have these issues. The HTC Desire has the Sense UI which seems to lag behind upstream Android releases quite a bit. However, some people greatly prefer the Sense UI to the stock Android UI, so there is a trade-off to be made there.
I would go the HTC desire. You can run it on telstra's 3.5G networks and get the true 21mbps speed over 3G. The nexus one is sold online only here - so servicing would be through visiting one of the limited HTC centre's. Buying a desire from Telstra gives you repair/help etc at every telstra store. Yes the nexus one currently has an android 2.2 update and the official HTC desire upgrade won't be till september - but there is already an unofficial ROM for 2.2 on the desire people are running.
I own an HTC Desire and I like it a lot, it is comparable to the Nexus one the tow things I am missing are the trackball and the Google experience.