The proper ceramic media probably does a better job. The microscopic pores in the media provide the max area for bacteria to grow on.
Having said that, the 'scoria' type volcanic pebbles will work too, maybe not quite as well, but they are cheaper, so you can buy heaps of them. Great for a big sump filter where you have heaps of space. Just soak and rinse them well before you use them. You can stuff your filter full of nylon pot scourers too, they work fine as well.
Cheers
Ian