What are the first moves chosen (White), by brute force chess engines? Title says it all. Feel free to add comment, theory, or explanation. 

Just to clarify, this is only regarding turn 1 of White, and no proceeding turns after it.
Houdini 1.5 on my old machine (1.8 G 2 cpu) slows down a lot around 20 ply (10 moves).

At 20 ply, it seems to slightly favor a four knights queen pawn game, starting with d4 or Nf3 over the Four Knights (1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6)

it switches at 22 ply to the Ruy Lopez Berlin (1.e4 e5 2.Nf3 Nc6 3.Bb5 Nf6 4.O-O Be7).

at ply 23, it switches back to d-pawn four knights, but starting with 1.Nf3