I often hear, "You should only pick your wedding photographer if they use a particular brand of camera/lens." (Usually Nikon or Canon.)
In March 2014, I was introduced to the Olympus OM-D-EM micro four thirds (M4/3rds) camera system, smaller and lighter than my Canon kit but with equally good image quality when using professional lenses from the likes of Olympus, Sigma and Panasonic. According to Olympus, the EM1 model at the time was designed to out perform the DSLR and is splashproof, dust proof but unlike the Canon system I was using, freeze proof down to minus 10!
I dipped my toe into the system but kept my Canon kit at the same time. However, in November 2016, I finally took the plunge and now exlusively use the OM-D system. My main camera is an Olympus OM-D-EM1 MKII with an Olympus 17mm lens which has a fast aperture to enable me to make the subject "pop out" from the background - this is known as bokeh, a Japanese word meaning out of focus. As my second camera, I use an Olympus OM-D-EM10 MKII with a Panasonic Leica 45mm Macro lens which also has a fast aperture.
This lens is also perfect for closeup shots of the rings, cake etc., and head and shoulder portrait shots and Leica have a reputation for producing outstanding quality lenses which in turn produce high quality images.
I also have an Olympus 14-150 zoom lens for those long shots from the back of the ceremony room/church or for capturing detail. Thinking back to film days, this has an equivalent focal length of 28-300mm and the other two lenses equate to 34mm and 90mm respectively.
So if my images have a "blurry background" this is done entirely for artistic reasons such as the image of the bride and flower shot and the groom in the mirror. The same goes if I cut heads off, this is to emphasise a particular detail such as the bouquet shot below.