well, you get some you lose some.

for example comparing my Canon 550D to Olympus EM10, both have their own strengths and weakness.

In comparison

Canon 550D
-better grip and ergonomics, since button are spread apart further away than small mirrorless
-faster write speed or buffer? even shooting RAW, the process of taking the image then previewing it is instant, where with the olympus I had to wait 2 or 3 seconds
-OVF, means even using flash in M mode, I have a bright and clear viewfinder, where the EM10 darkens until almost pitch black as it previews the exposure
-cheap lenses, I have the good Tamron 70-200 for below 2k but with m4/3 system, the closest equivalent is the panasonic 35-100 which is 3k+. most dslr lenses are cheaper than mirrorless too because of the age.
-battery life is crazily good, I got 900 images in a single charge from the 550D before although it is rated at 500-600 shots only, since you can turn off the preview/screen that uses a lot battery.
-noisy shutter. it varies from different dslr, but the sound of mirror flipping is extremely annoying if you are photographing concert or street which always unwanted attention.
Olympus em10
-well, the size and weight is nothing compared to a dslr, very light to carry around and hanging on your neck/ hand, less tiring for long time usage.
-in body stabilization, a very big advantage compared to dslr, I did some experiment before, got very good results of handholding the camera for 2 seconds at 24mm. put any lens on the camera and you still get stabilization.
-EVF, a lot bigger and more functions can be shown. with dslr you get very small viewfinder on entry level models with basic information of exposure only. with EVF, you get tons of information like leveling/ peaking (good for manual focus)/ various grids to aid composition/ previewing images and even recording video using viewfinder.
-resolution of EVF, as good as it goes, a EVF is basically a smaller LCD. you don't get the same kind of feel like a optical dslr, just like looking at a image on your computer and seeing it in real life. you get a little lag when pan around or subjects moving around, then the colors are a little off compared to real life.
-good quality lenses. although more expensive, more mirrorless lenses are built in a good quality since they are newer. almost every olympus lenses have good performance regarding kit lens or pro lens. the aperture plays a role in separating the pricing rather than sharpness.
-battery life is quite poor, I got maximum 300 shots with the camera which only lasted for less than half day. with wifi those functions turned on, it gets even worse.

Image quality wise, they are from different formats so comparing them aren't really fair. hope you can understand my not so professional kind of writing and comparison.