I would vote, but I have no actual experience with calcium or kalk reactors on my tanks.
In the research I have done on them in the past it always seems to focus on the horror stories. Most revolve around clogged ports, system over runs, and the tedious process of getting them dialed in. There are success stories out there though and I am sure they are plenty.
I do know that I have seen 2 tank disasters personally with one being a calcium reactor and the other a kalk reactor that fried the tanks.
As far as the questions you posed of
Safety? Simplicity? Cost? Adjustability?
. I can say that the complexity of setting up a calcium reactor and the need for constant checking of the kalk reactor were what chased me away at the beginning. Not to mention the upfront cost. I understand I may be better off in the long run cost wise, but it hurt too much in the beginning to justify it at the time.
I wish you luck in whichever route you decide.
John
"Critics are men who watch a battle from a high place and then come down and shoot the survivors." Ernest Hemingway