Linux or windows ??

Hi,

I am planning to set up a network of approximately 200-300 machines and one of my colleagues is suggesting that we should set up a Linux network and forget about windows completely. The reason for doing that is because of fees for licensing microsoft OS. Is this achievable or is it a wishfully thinking?
Is Linux (red hat 7.2) better than window2000?

Please suggest !!

Regards,
esng