Yeah, the First of group loop with the null boolexpr is the fastest way because it doesn't run the boolexpr once for every unit, but remains in the same function, efficiently switching between units. I think it's about a 35% speed gain according to Anitarf's tests if I remember correctly. But this is the average, the number actually ranges from about 10% to 9001% depending on how many units are on the map. (Group enumeration inside Warcraft III is done with a Quad-tree if Nestharus' prediction was correct)