“Isn’t MO technology the same as the Minidisk? Why do so many pros use it?”
Magneto Optical (MO) discs have several things in common with Minidiscs (MD), the main one is that they both employ the magneto-optical technology whereby data is recorded through a combination of a laser (used to heat the data surface) and magnetism (used to polarize the data particles). Playback is then done through a low power laser. But their differences are significant. First, a MO disc is much larger and has a much greater capacity. MO discs also use CLV recording. This refers to Constant Linear Velocity, which means that the rotational speed of the disc is altered depending upon where the laser is on the disc. The rotational speed varies to keep the linear speed the same at all times. This is the same way a CD works.
The reason some pros like to use MO media is because it is very durable and has an extremely high degree of data integrity. There is also the convenience issue. If you record directly to a MO disc you can simply take it out and put it on the shelf for safe keeping. There’s no real need to ‘archive’ or back up the data. MO discs are also great for archiving data from hard drives. They are quite fast (for an optical drive) and can hold several gigabytes of data.
The major downsides for MO are cost: it’s relatively expensive to operate, both in terms of media and drives, and while it’s relatively fast you certainly can’t record 24 tracks of 24 bit audio to one drive. In fact very few people record more than eight tracks to a disc. It’s most commonly used in certain types of post production work where there the track count is not high and there is no time to archive any data.