You make it seem like the entry-level Nikons are made of biscuits, and the pro-Nikons are made of some indestructible material
Whilst I'd certainly agree that the pro bodies are built tougher, i doubt the difference is as drastic as you make it out to be. The kind of impact that can cause a D90 to crack would likely not leave a pro body unscathed either.
The countless numbers of entry-level Nikons still in use (eg D40, D60, D70, etc) should be testament to their decent build quality.
Agreed. I have owned a number of plastic body DSLRs and a magnesium one.
Speaking from personal experience, if you drop a DSLR from any height above 30cm, it doesn't matter whether it's a rock solid EOS 1D or a full plastic D3100. The only thing that's going to save the camera is how lucky you are. If it hits a concrete pavement or a random stone directly on the LCD, even a EOS 1D's LCD will crack. If it hits the body, there will definitely be a dent in it. And if you really just suay, and it hits the lens head on, the mirror could just break too, even if it's a D3x.
The only advantage of a magnesium body that I can see is perhaps that the Magnesium body DSLRs are higher-end, and therefore more ergonomically designed, and easier to grip. (After all, you pay so much, they have to add some improvements right). And also, Magnesium bodies tend to be water-resistant, but then again, do you really need it? And even if you have it, do you really want to try your luck with a $1000 camera? Some people will of course Need it. But if you don't, then it's not that much value-add to your consideration.
Plastic bodies are just as durable as long as you don't take your DSLR to the African Sahara everyday.
Of course some people prefer to have a "tank" build, and that it "feels more pro". But that's personal preference. Honestly, I rarely look at the build of the camera when I buy one. I normally just look at the image sensor, low-light ISO, AF-system and the suitable lenses. I'll admit that as illogical as it is, it does "feel better" to use a giant sized EOS 5D, than a tiny D3100, but you just have to bear in mind that, that alone doesn't help you take better pictures.
All in all, if you can afford it, and can spend comfortably, just get the d300. You get the wholly illogical shiok feeling everytime you hold it and press the shutter.
If you are on a tight budget (and who isn't), just get the d90. You don't get any "pro feeling", but it takes equally good pictures.
