continuous dosing

Im about ready to start dosing saturated kalk to my 65 gallon reef. Really only need a single head, trying to decide between these 2 dosing pumps. My plan is continuous dosing at a very slow rate throughout the day. May try only at night. We will see. But which would you pick and why?

Since R2R has been such an amazing source of knowledge for me through out my years in the hobby I want to share this idea with you all. It was originally posted under the chemistry forum for discussion but this has now become quite the DIY project and I think this is a more appropriate place for...