Tubipora propagation - rock or sand bed?

[Smarkowiak]

Recently acquired a nice blue polyp tubipora species from LFS. I am leaning towards fragging it and initially I was going to place the frags spread out on a large rock I wanted them to encrust but now I have noticed that a small polyp broke off, settled in the sand (caribsea aragonite) and is growing pretty rapidly. Should I instead place the frags in the sand and let them grow out there?

Aesthetically I think either option would please me, so I'm just wondering which environment you all think the coral would do best in?