[Aldric]

I think it would depend on what I was going for:
Ant-man uses growth (and shrinking), the Hulk has an alternate form. If you still look like yourself, only larger, growth makes more sense, whatever the point cost may end up, alternate form is for when you want to become something else.

And regarding the ability to break through walls, I think it's worth noting that, barring some very strange buildings, you could already break through by punching the wall, eventually.
But I would probably change it