Which HDD for system

All these drives are manufactured by the same company there isn't much room for differences, especially when some of those drives are the same model just with a differing capacity.

Additionally "best" is vague measure. Do you mean in terms of performance, reliability, size?

Samsung f3 7200rpm 1Tb
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Performance & reliability(are most important), the size & price are all a factor. I listed just WD drives 'cause I never had any problems with them & have been using them for years, but I have heard good things about the Samsung Spinpoint F3 too.

Get the (WD5001AALS) if you have a SATA II mb.
And get the (WD5002AALX) if you have a SATA III mb.

Which one has the highest platter density & how many platters?
Also, if someone has a suggestion on HDD other what has already been listed, it would be very welcome.