I have and use both mirrorless and dSLR. Each has its strengths and weaknesses.
For life and nature photography, where there is no FAST action/movement, a mirrorless is fine.
For fast action (basketball, soccer, etc), I use a dSLR, as it works better for that.
For difficult lighting, I prefer a mirrorless, because of the Electronic Viewfinder.
Mirrorless used more power than dSLRs, so you will need to carry more batteries. This is a major logistical consideration for travel; I need 3 to 4 batteries with my mirrorless to shoot a full day, whereas my dSLR will go 2+ days on one battery. Flash is NOT used.
For my travel camera, I use a mirrorless Olympus Micro 4/3 camera. It is about half the weight and bulk of my comparable dSLR. But I have the battery hassle.