The design of bio-balls with all of there little bumps and spikes help them break the incoming stream of water down to drops of water when used in a trickle filter. Many types of media designed to be submerged will not break up the water stream and you end up with channels of water flowing through the media, so some media gets a lot of water contact and much of the media doesn't get hardly any water contact. This is why I like bio balls for trickle filters.
Pretty much any media will work in a trickle filter though. A good trickle plate that breaks the incoming tank water up into a LOT of different streams will help spread the water out more evenly over the media which will make it more effective. I have even seen some rotating bar configurations for trickle filters where a bar constantly rotates over the media to help keep the water from channeling though the media.
If you already have some media you want to use in a trickle filter... go for it! If you are buying new media my preference would be the bio balls with the pointy spikes on the outsides. The ~1 inch diameter bio-balls seem to me to be about the best size for breaking up the water streams with the way I have my trickle filters configured and with the particular flow rate I have.
To me bio-balls aren't all that great for use as submersed media. There are other medias that have much more surface are for their size. Even very cheap lava rock should have considerably more surface area than bio-balls.