Having a phone with a very large display like 6" isn't necessarily a good thing. One of the main problems I have with those large phablets is that they are very uncomfortable to hold, let along using then with one hand. Obviously it depends on the size of your hands. People with large hands will obviously won't have any problems with that, but people with smaller hands will find it uncomfortable holding the phone in one hand and operating it with one hand. I found it sometimes uncomfortable to reach the other side of the screen, like pressing icons on the far left side of the screen when holding the phone in the right hand. I just use my second hand instead, which is not really the experience I am looking for when using a phone.
When playing games in landscape orientation things are better because you hold the phone in both hands and can easily access the entire parts of the screen with each hand. This is one reason why many people prefer buying phones with a big screen, so they can have a better experience playing games. If you are not among those who play a lot of games, you probably should ask yourself whether you'll really benefit of owning a 6-inch phone or maybe it will be better to search for a phone with a smaller screen size like 5.5 inch one, which are still pretty big, but not as big as the 6-inch ones.
I think that many buyers sometimes overlook this issue when they order a smartphone online and not testing it first hand. Furthermore, you also might find it uncomfortable to carry around in your pocket because the phone is so big. I have a friend who has the Gionee M5 Marathon Plus that also has a 6.0 display and he found it very uncomfortable to operate and carry around.
Here is a video by FeekyArif that showcase the phone so you can get to see how it looks and feel when holding it in both vertical or horizontal orientation.
I think this is one of the disadvantages of a large display, but obviously it also has its advantages alongside it.