Fab, I was hoping you would say that. I have both but just about to set up my new tank so think I will just use the vacuum for the bigger one and not worry about the under gravel plates for now.
I thought the under gravel plates would make the gravel cleaner but the guy in the shop said if anything it would make it dirtier and the vacuum would clean it up. He said the gravel filter just stopped the gravel from going black and smelly....which mine never has done anyway.
I dont use them, get a gravel vacume though (if you havn't already got one) and vacume the gravel when you do a water change, i'm alwas shocked by the amount of poo and un-eaten food that sits in the gravel. I think you deffently need one or the other but personaly i would go for a vacume.