Real Plants are better. They filter your water.
chaeto is best, because it cleans the most, same with culpera, but Culpera will most likely be eaten by tangs and rabbit fish ect. Chaeto tends to get a little ugly in the display though, it loks like a mass of fishing line.
I tend to like Shaving Brush Plants and Mermaid plants. They are single stock plants and are not invasive. Culpera grows on runners so it's invasive, chaeto wont attach to anything.
Plants wont be a problem to corals, but if you go with culpera then make sure you keep it well trimmed.