This is the question Artosis asked here: Twitter.
I facetiously answered hold position, because I always use hold when I do a run by with lings in team games. With my limited APM, I found this most helpful to get some damage done. But at high level games with enough APM to respond quickly and either move workers or get attacking units in time to defend, it will be different.
So I accepted the challenge when Artosis replied back with a request for a link.
I decided to go into Unit Test Map by SuperFerret and test Attack, Hold, Patrol with these units:
21 Workers for all Three races on minerals.
4 Zealots (no charge)
8 Marines (no stim)
6 Speed Lings
Each unit had 10 seconds to kill workers, this time is arbitrary and allows most units to get a few attacks off. Also the count of units is based on:
1 DT, usually keep them separated to maximize scans and your investment.
4 Zealots, enough to carry in a warp prism.
8 Marines, medivac.
6 Speed Lings, enough to not merit a large investment and a good counter when opponent is moving out.
Now the map has a different mineral patch setup than other maps, but figured with 21 workers it would create a good saturated scenario. The test has these standards:
Hold position was directly in the middle of the worker line where it maximizes amount of potential kills.
Attack move was done by moving next to base, then attack Move from left of base into the middle.
Patrol was similar to attack move, from directly left of base to patrol to the right and back in the middle of mineral line.
Below are my graphs to show which is best.
With this graph in place, we can come to these conclusions from the test.
1) Range units are ideal, probably 4 hydra's in an overlord will do more damage then 6 slings.
2) On ROI, 6 slings are the best, marines second, and 4 zealots third. (Based on 150 minerals for 6 lings, speed 100/100=250/100. Marines = 400+100/100=500/100)
Now this statement needs an explanation. DT's while probably having the biggest ROI potential, in a controlled environment was not the most cost effective with all the tech cost associated with getting 1 DT to a mineral line.
3) Attack Move and Patrol will generally be the best choice, now I did notice that hold position caused more units to be damaged than attack move, I do not think it's that relevant to this testing.
In closing, using attack move after getting units into position will be the best choice when dealing with ranged units and normal saturation. If an overly saturated based and melee units, hold position will be best.
This is my first informative post, so hope my organization makes sense. Any feedback much appreciated.
edit1: Changed graph to have a legend, so easier to read. Amove/Patrol are essentially the same exception of Speedlings.
edit2: I realize I am a nooblet, this does not answer Artosis question, I will now work on that as well.