What is the difference between Mobile Device Management and Over The Air Method?

I have gone through a number of questions regarding the mobile device management and Over the Air method but I did not get what is the exact difference between the two.What I got from study that OTA was used previously and was replaced by more effective MDM.What I want to know is what was the need of MDM when OTA was there or Why OTA was replaced.Can I use the OTA server for MDM installation?

I have gone through a similar question but didn't get a satisfying answer so I wanted to ask for a fresh one.

Solution

OTA was old way and it was limited:

It allowed only manual installation of configuration profiles (you can't automatically push any new profiles
It was limited to profiles only (no commands)

MDM is the new way. It allows

Automatic installation/upgrade/removal of profiles (when your device is enrolled already)
You can issue commands (like Wipe)

A lot of MDM vendors use OTA to bootstrap MDM (install a configuration profile with MDM payload to a device) and later on they use MDM for the rest of device management.

Update 1

Generally OTA is used for couple of reasons: a) To authenticate user b) To authenticate device (that a client is iOS based device) c) To distribute initial MDM profile

Item a) and c) could be easily done without OTA. You can have just a web server which will use some form of user authenticate and will return MDM profile.

And I don't think that you can solve b) outside of OTA.

If you go with OTA, you will have to implement all three phases. Phase 1 is most flexible (you can implement a user authentication different ways). Phase 2 and 3 are very strict.