While we're generalizing people's takes, I feel people are comparing Nils too much to preseason hype and to other prospects rather than observing him as he is and for what he's doing. I don't have any problem saying Jones has played better than Nils, but I think Nils and Jones are really different players as well and offer very different things to the team at this moment.
Jones has excelled and I'm very exited to see him resemble Fox so closely. He looks like a GEM. At the same time, I've seen him struggle to contain players in the d-zone this preseason and sometimes his anticipation of where the play is going ends up with him in a tough spot when something falls through. Schneider as well had some notable gaffes with the puck on his stick and has some clear limitations right now from a puck movement perspective.
Nils OTOH has showed a knack for sticking to his coverage and closing gaps really well. He also looks adept at leveraging himself in tight and getting under forecheckers and net front forwards to cancel plays or escape pressure. He's also put up points which I don't think should be shrugged off. Even if Jones has been more noticeably good, there's something to be said for a defenseman you don't notice--especially when they end up on the right side of the scorecard, which Nils has done each game.
An NHL coach might be inclined to prefer that player at the start, and I won't be angry or find it unreasonable if that's how it shakes out. Based on what I've seen, I'd like both on the team, but I think Nils would be my pick too based on what I've seen. Not because I've ever been that high on Nils (got lambasted months ago for proposing to trade him for Larkin), but because I think he's played well--even while I think Jones has played better.