In my opinion it mainly depends on what you are going to use the hard drive for??
If for example you are planning to use it for video editing or other high bandwidth tasks, I would not suggest using a network hard drive.
However if you are going to be using the hard drive to simply store files and would like to have access from the other computers. The network hard drive will be your easiest option.
If you need anymore help, dont hesitate to ask.
It will mainly be used for storing music etc on, and backing up files on the other 3 computers, thats why I thought a network one might be better.
Right thanks guys, probably going for the network one instead then, should be more useful I think, plus lets me share peripherals etc, which is always good.