Miltank with Greninja or Butterfree

I have been running a miltank in my crobat/girantina deck, and it has been doing really good, and I wanted to make a deck based around miltank. I have narrowed down the stage 2 choices down to Butterfree and Greninja. Butterfree has the advantage of a fast setup with adaptive evolution, but Greninja has the shrukin whih makes OHKOs easier. I’m leaning towards Greninja, even though it’s slower, it uses a very small amount of energy which allows the spammage of water shrukin. Suggestions?

I don’t think Butterfree is worth including. Greninja or Empoleon/Dusknoir are my favorite partners for Miltank.