The problem, though, is that Lindholm might have gotten top 4 minutes, but his actual responsibilities was a bit more varied. He was a bit more sheltered, at times, than you would expect a top 4 defenseman to be. That's the norm for a rookie, but it's a bit misleading to just call him a top 4 guy right now. If you assume you've got Fowler-Vatanen out there in more favorable offensive roles, that means Lindholm has to carry a much heavier load defensively, and to be frank, he just hasn't proven he can do that consistently.
Vatanen was simply the most sheltered defenseman we had, and by far. All that stuff about Anaheim putting more shots on net really needs context, because he was effectively spending the vast, vast majority of his time in situations where the Ducks would put more shots on net. You can't just expect to give him 20-25 minutes a game, and expect that to hold true. While you can say he contributed to putting more shots on net, you can't ignore the situations he was on the ice.
As far as the question is concerned, the answer is easy: Lindholm and Fowler. Fowler is the only one of the three who has actually seen top pairing responsibilities, and who has shown he can handle 20+ minutes a game without needing any sheltering at all. Lindholm comes a distant second, having seen actual top 4 responsibilities at times, and he's shown he can be an effective two-way defenseman(again, at times). Sami is a very distant last, and right now he's basically a 3rd pairing offensive defenseman. I expect this all to change, with Lindholm and Sami both earning more responsibilities, but let's be honest here... any top pairing that includes either of Lindholm or Vatanen is questionable, at best, as of right now. Lindholm would just be less questionable.