there's no difference, LR
rubble traps waste just as easily if not easier and it's harder to clean. I would stick with the bio-balls, many have negative opinions about them, but if you take them out every once in a while and put them in a bucket of tank water from your PWC
, grab a handful at a time and shake them in the water, you'll loosen any debris.
If you want expanded bio-filtration in the sump, just put some bigger pieces of LR
in there. The larger the piece, the more low-oxygen area, the better chance for denitrification. At least, that's the way I see it.