To rock or not rock: Rocks in a sump?

[WhatCouldGoWrong71]

I have been dark curing gulf rock for almost a month now. Ammonia hit zero this week, so it's time to start putting this together. In looking at tons of sumps it is interesting to see that it would appear to be a 50/50 split on people who put rocks in their sumps vs. not putting any rocks in their sumps. What is the rationale here? I have a 135G system that has been running for >4 years and I have lots of rocks in the sump. I could easily use that space for something else. Is it that there is enough beneficial bacteria in the display, in established tanks, whereas you don't need it in the sump as well? This setup already fights low nutrients (nitrate is currently at 3.5 and phos .11). My new tank is smaller, thus having a tighter sump. While curing the wet gulf rock, I took about 8 pounds of bio media that was seeded in my other tank and placed that in the new sump for purposes of helping cycle. If I could go bare sump, just equipment, that would be ideal. The display is 60G (ish) and I have 80ish pounds of live rock from the gulf in it. Likely too much frankly, or so my wife has been saying. So what is the correct way to create a sump, with or without rock?

 

[MoshJosh]

The only bio filtration in my sump is a large rock. . . the largest I could fit!

 

[shakacuz]

some tanks run oversized filtration which reduces the need/desire of extra rock.

 

[Mr. Mojo Rising]

I keep rock rubble in my sump, my rationale is:
-extra surface area for nitrifying bacteria
-act as a safe place for copepod breeding
-I use some rubble sometimes to glue some frags onto, since the rubble is populated with bacteria, it won't be an algae magnet when put in the tank under lights.