Which...is what I said I thought.
I like your tree analogy, but I take the stance that we need to do both, in a way. Execution shouldn't be an option at all UNTIL our justice system is fixed. That goes all over the place, from NY Rockefeller drug laws (thanks, NPR) to Texas judges itchy to tie a noose.
I'll toss in my own analogy here. You want to make sure a car doesn't fall off a cliff before you build a bridge. Stop the traffic while the work is being done. They're part and parcel to one another. Building that bridge, in this case, is going to take a ton of work and while that work is being done, CP should NOT be an option. Incarceration for (alleged) violent offenders is much better than killing them, and incarceration for even those wrongly accused is better than killing them.
Again, I'm FOR the death penalty, but we cannot execute a person the way our justice system currently works. It needs to be off the table until we get there.