Grass density group vs individual

[I’m a noob]

Playing about with speedtree and of course the fire thing I make is some grass… because, well… I’m lazy.
The question suddenly occurs to me…
(Example: I want 20 clumps of animated grass on my floor).
Which is the most efficient (cost wise) method?
1: a large group of 5 clumps in one static mesh repeated 4 times.
2: a small group with 1 clump in 1 static mesh repeated 20 times.