Photographers love thier gear. It's paramount in the process of photography. They will love certain pieces gear, and will hate others. With that love and hate comes feuds and bias. There's fanboys of every brand and feuds about every piece of gear. The debate between mirrorless and DSLR cameras has been going on for around a decade, and each side has their crowd.
I will admit that I love mirrorless cameras. Here though, I will attempt to be as unbiased as possible to give you a good idea on what form factor you should lean towards.
The most distinct difference between the two is how small mirrorless cameras are compared to DSLRs. Because mirrorless cameras have no pentaprism and mirrors, their footprint is drastically reduced, allowing them to be more portable and convienient.
With the size reduction comes different ergonomics. DSLRs heavily relied on their size for grip, with their large, distinct hand grip. As mirroless cameras are smaller and slimmer, the hand grip is less pronounced to preserve its small form factor.
With the removal of the optical viewfinder in mirrorless cameras require an electronic viewfinder (EVF). It uses the live view feed coming from the sensor and displaying it on the EVF. The EVF allows the photographer to accurately determine the focus using focus zoom and focus assit features. Since it is an exact replica of what your camera will be rendering, it helps them determine the optimal exposure before taking a shot.
Due to the miriad of new technologies in mirrorless cameras and the smaller size, battery life is multiples shorter than DSLRs. The power required for the two displays and live view sips a lot more power than a single static screen and optical viewfinder on DSLRs.
Mirrorless cameras have the advantage of no moving parts required to take a picture, and it reflects in their specifications. They have faster shutter speeds and higher continuous shooting modes than DSLRs, which is beneficial to action photographers.
Despite the increased technology use in mirrorless cameras, the moving mirrors in DSLRs are wihtout a doubt more prone to failure over its use. The mechanism will wear down eventually at a faster rate than the new technology found in mirrorless cameras.
DSLRs are not going away any time soon. They have their use cases and mirrorless cameras have theirs. There is no clear winner. It depends on your use case and what you expect out of your camera. You want an all-day camera that will be comfterable for long periods of time? Invest in DSLRs. Do you travel constantly and want a powerful camera in a small package? Then get a mirrorless. It doesn't matter what people are saying you should get. It matters how you will use your camera and what you are comfortable using.