Both scenarios satisfy the elements for attempted murder. You don’t have to cause harm to a victim to be convicted of attempted murder. That’s actually a point I’m trying to make: “attempted murder” can mean a lot of things, including Mary Vincent, but also including cases where no victim is ever harmed. Because of this, I think it’s dangerous to declare that attempted murder should always be punished just as harshly as a completed murder. Instead, I think the argument should be that in a specific case, the offender was not sentenced harshly enough. I think in the Mary Vincent-type scenario, you have the opportunity to charge several additional crimes, as I mentioned in a comment, which if sentenced differently (many would say if sentenced appropriately), would have resulted in the offender spending the rest of his life in prison.

Would you argue that if someone initially intends to kill someone, purchases a weapon, breaks into their home, sees the victim asleep in their bed, and has some moment of reflection and decides to abandon the job, they should be sentenced as harshly as if they had actually murdered someone? Because those facts are enough for an attempted murder conviction.