Bn's are not too aggressive, more defensive. Algae does seem to stay away from my plants when they have some wood or rocks too grow on..
Regardless, I think eventually the scrubber would win unless you were using massive ammounts of ferts.
If you go to goldfish or discus forums you will find thousands of post of people who were surprised when the BN plecos they had for years suddenly started attacking their fish. Sometimes you get away with it, sometimes you don't. People theorize as to why, but if you read enough posts you begin to see that it's a crap shoot.