2 battle ship > 20 Burst Fire?

I would recommend against it. I thought about that too, but I opted for the extra second of freeze granted by Boost and 1 Torpedo. 1 Torpedo, if you hit at least 3 monsters (which you can and should do at the bottom right corner of Newties), it's much stronger than any other skill you have until you get Cannon to 11. While you're at it, you can pick up a point of Air Strike too.