I think it boils down to your own personal preference based on Size of tank, quantity and type of corals, and if you are able to schedule your life to dose when necessary.
First, what size tank are you running.
If you have a large tank with loads of corals, then you will want to dose and not rely on water changes to maintain your levels. If you have a small tank and do proper water changes, then you can either hand dose or you might consider kalkwasser in your ato to help keep your levels maintained.
Second, what type of corals do you want to keep.
Some types of corals use calcium much more than others. Then it goes back to your life style and if you can dose on a very regular basis.
Third, Lifestyle and free time.
Going back to how much you will need to dose based on size of tank and type of corals, can you set specific times during the day to properly dose the right mount of each mixture. Some people do and some don't. I for don't have that luxury and my fish are fed at all type of different times at night.
I currently run a 16g Nano and a 28g JBJ, but neither have that much in the way of coral. After I complete my 120g build, i will initially hand dose the tank to keep a better track of things, but plan to switch to dosers as i don't ahve room for a calk reactor. The consistancy if your parameters is a huge issue to corals and having a lot dumped in at one time a day can cause your parameters to swing. The dosers drip in small quantities, automatically, throughout the day.
There are plenty of memebers that do just fine with hand dosing so there is nothing wrong wtih that practice. I just need more automation in my life to meet my needs.
Best of luck.