Looking at the spreadsheet, it looks like Fenrir is the the raw damage option, while Blowout is more for control with the BB Reduction. If damage is all you need, then Fenrir should be your go-to, since it's also faster to charge like you mentioned
docs.google.com
Keep in mind that Fenrir's damage in the spreadsheet does not include the bonus damage from Bleeding opponents. So in reality, it's even bigger than represented