I have used both, MySQL has the edge on friendliness but Postgres is overall the better database. A dual or quad Opteron system with a decent amount of RAM and

I have used both, MySQL has the edge on friendliness but Postgres is overall the better database. A dual or quad Opteron system with a decent amount of RAM and well-tuned Postgres should be able to handle queries sufficient to drive a web site at 50 to 100Mbps continuous bandwidth, assuming no ridiculous queries.