I've gone through many dosing pumps and here are my judgments.
Medical Dosing pumps
Pros: Affordable, can add small amounts to large amounts, very precise, quiet, can do dual channel for 2 part, can have add on depending on which one you buy.
Cons: If you're like me you could only use the silicone tubing in order to do dual channel. However, silicone tubing seems to fail after about 2 months. Constantly replacing it is kind of a hassel. Also, one of your channels might fail before the other but you wouldn't notice unless you check everyday. You could be adding 10ml of part A but adding no part B.
I had a problem of it holding siphon after about 2 months, but this is probably due to the silicone wearing out. You can use norprene instead of silicone which would definitely up the tubig life span but than you wouldn't be able to fit two channels on the roller.
Mine had to be ran 24/7 and if the power shut off, you would have to turn it on again. However, I know some automatically turn back on to it's programed setting so maybe mine wasn't the best.
Overall, I give a medical dosing pump a 3/5. Also, I would probably not go this route again unless I bought two medical pumps and used the norprene tubing.