Sump questions

[DanG]

I'm looking at getting a sump for my next tank and the LFS I go to has a sump that has a sheet of black plexi in it that sections off a part for the refugium. Is there any compelling reason to get the refugium and sump in one box or is it better for them to be seperate? Or is there anything stopping me from dumping a ball of macro into a regular sump without the division?