Which kind do you prefer and why?
I prefer Matte. Glossy monitors and screens are too susceptible to annoying reflections in the environments where I normally use them. Also, after hours of use a matte monitor is more restful on the eyes. A glossy monitor makes a good first impression, but that's about it.
One has to wonder whether the days of the matte monitor are numbered.
If you look at cellphones, tablets, and increasingly, laptops, they've all got glossy screens.
Monitors use for long continued work are different from cellphones and tablets. I love the glossy screen on my cellphone - great for photographs, but I do have trouble using it in bright sunlight. I recall often looking for a shady spot using my phone map on a sunny day.
Only Apple takes glossy screen reflectance seriously.
I've got a Surface Book and it has much higher reflectance than my years-older MBP.
Same with my phone: my Nexus 6 shows far more reflections than any iphone from the last 4 years.
And the latest iPad Pro looks absolutely phenomenal in bright sunlight, despite being glossy.