Recently I got my self a Sony A7II full frame mirrorless camera. I'm a Canon user by the way. If money is not an issue I would have gone all the way Canon and buy the 5D MK4 but at $3,000 or more, that's not going to happen. Plus the fact how photographers are being paid these days it's a steep climb to get back that "Return of Investment" (ROI) or most probably it would be charged to experience.
My current Canon gears are 7D MK2 and 70D. My set-up are intended for mobility since I do a lot of events and on-site. For me Flash-Photography is important specially for small-item product shots and onsite editorial portraiture. I got myself 2 600EX-RT, 430EX RT and ST-E3 RT Wireless Remote trigger. I’m sure there are no easy-to-use equivalent that I can buy for the Sony Alpha system. At best I got the 3 units of CACTUS VII transceivers (one is VIIs for Sony) so that I can use my Canon Speedlite Flashes to work with Sony A7II. The CACTUS VIIs, you mount it on top of the camera hot-shoe and the 2 VII (basic) is for the Canon 600EX-RT. I used it a couple times but the operation and intuitiveness is not as easy as all-the-way Canon.
I’ve read reviews and seen YouTube reviews how some gears and other ad-hoc accessories set-up would do the trick. I’m sure it would, just not effortless.
I’m also not to keen on the handling of the A7ii when a bigger lens is attached to it. In my opinion DSLR are still the best all-around system for photographer in consideration to handling, all-situation photography and budget wise. Not all photographers can afford a Full-Frame (FF) and those f2.8 trinity lenses. I got a Sigma MC-11 (Canon to Sony F-mount adaptor) to use with my favourite portraiture lens right now which is the Sigma 50-100mm f1.8 DG HSM ART. When this beast is mounted together with the MC-11 it’s quite heavy front end. I’m sure for events like wedding having two Sony Alpha series camera set-up is quite uneasy to go around not like using 2 DSLR. Anyway to each his own. There would be some who would vouch that the light-weight is a better feature than handling.
I’m probably will continue the crop-sensor (DX) format as my main gear until to the point that my photography paid-gig can justify going Full-Frame (FF) all the way. As for my A7II I got this for my everyday camera. Though the operational intuitiveness is crappy, the Low-light and Dynamic-Range performance is very good.