In my case I have both. But if you don't have issues with low pH when using a calcium reactor alone, then I'd shut down the kalk and just go with the calcium reactor (less hassle).
Basically, for me it comes down to cost and ease of use.
B-ionic is expensive, but if your tank's demand is low then it's workable. It's a bit of a hassle to dose on a regular schedule.
Kalkwasser is dirt cheap, but is limited to the volume of your tank evaporation. It's a bigger hassle to mix/dose then B-ionic, unless you set up a kalk reactor. With a reactor there's very little hassle.
Calcium reactor is expensive to set-up, but once that expense is made there is very little ongoing expense (2-3 bottles of CO2 at $10 each and a recharge of substrate, $15 each year). Petty much unlimited calcium/alk delivery using one. Very little hassle factor.
Edited by jfinch