Microfibre has an open structure which holds more paint, giving the roller better performance, better paint pick-up and release.
Better release means you get an even coverage, noticeable from the first coat.
Microfibre is suitable for all paints.
Microfibre is lint-free and doesn't foam.
It's a good idea to use a new roller for each job, especially if you're a DIYer and painting a ceiling. The nap on the cover gets compacted with use, especially at the open end where the roller frame attaches, and results in a striped effect. This problem is particularly pronounced when working overhead, such as when you're rolling the ceilings.