Whoever is most willing to collapse the US economy in order to get what they want. Right now there's a couple Republicans who've suggested they don't care how far this has to go to get what they want, and when asked what they want, it was "I'm not even sure."
I think it's pretty clear that I think Republicans are wrong for doing this, but not because I think Democrats are right or better, but because this isn't supposed to be how the government is operated. You shouldn't get to say "This law that was passed and signed a couple years ago doesn't work for me, so remove it or we fund nothing." There's a way to do things and if there isn't enough support to repeal a law, then extortion is not justified.
The sociopaths in this case are the few (very few) Republicans who have said they don't care how long this goes on for, so long as they get something out of this. When asked what they want, they said "I don't even know." Most Republicans are trying to do something to end this, but the government is absolutely right for not allowing a precedent to be established where laws can just be defunded.
The administration and the senate has made it clear that if the house submits a bill that does not defund the ACA, it'll pass immediately. All Republicans have to do to end this is say "We'll defeat the ACA the way the government and constitution are set up to defeat laws we shouldn't have - by passing a repeal." But they're not.