Oh, not for any good reasons other than I was a reefing newbie at the time and my LFS recommended the Red Sea doser along with the Red Sea 4-part for dosing simplicity. And that wasn't wrong. The Red Sea dosing lines and 4-part are even color coded for newbies, and the fixed dosing ratios of the 4-part made sense for me-who-knew-nothing at the time.What made you choose the Red Sea Doser instead of the DOS?
Now I use the Red Sea doser for dosing the NYOS 2-part, and use the other two dosing heads for dosing nitrates and phosphates, and its rock solid. I just check my Trident ACM and NP testing results every couple of days and adjust the dosing amounts as needed.
And I have a DOS for doing auto water changes, which also really stabilizes my parameters even more.