You get lots of mixed opions from inexpensive Clone dealers.

Sometimes the cheapest does not always get you far. Although I have several friends who started on the cheaper plastic one, the metal versions seem to last longer.
If you think your gonna tinker, get going then go bigger, sure, plastic may be fine. In the end, if your a beginner, you crash and you end up replacing more plastic broken parts than on a metal head. That's been my experiance dealing with mine plus other people's.
I've owned up to 5 (have 3 now) 450's and have built or setup about 15 of them for friends and just aquantances.

Here's a bang for the buck list of parts:

[link=http://www.mycoolheli.com/450RecommendedSetup.html]Clone 450 setup[/link]

Depending on how much you spend (batteries etc), you can often find some of the parts cheaper at [link=http://bit.ly/9zFxM2]HobbyPartz[/link]