The biggest improvements in the last few years have been in dynamic range and being able to take photos in darker and darker scenes.
I think the easiest win now is getting top-quality (not necessarily new) lenses. Newer lenses can be worse in some ways. They've generally traded build and image quality for the convienience of auto-focus and zooming.
I've had my photography written off as useless after people found out that I used a 12MP camera (a D3) - only to have the same people look at some of my prints (made from D3 raw files, carefully processed in Lightroom), ooh-ing and aa-aahing over them and wondering what camera I used to take such wonderful photos.
(Then again, for a really big sensor, I bring out my Fujica GL690 - a beast of a rangefinder in 6*9 medium format.)
> It managed to pull me away from the Canon 6D I’d used before, and I haven’t looked back
In any case, that review didn't really contain enough _technical_ detail to make the comparison to the 6D seem fair. Heck, even dpreview's first impressions contain more information: http://www.dpreview.com/reviews/fujifilm-x-t2-first-impressi...
In what way are they not the same category? They cost the same, are used to the same thing and target much of the same audience. The only difference is they make slightly different design trade offs when it comes to viewfinder and sensors.
If your camera can do clean images with 100,200,400 ISO, then one more stop to 800 is a huge deal.
If it can do 100,200,400,800,1600,3200 and 6400, another stop is no huge deal anymore.
Same goes for DR.
"because that's what's going to make a difference in your photo"
No.
It allows you to use shorter shutter time when needed. Like sports, nature, in a moving vehicle, etc.
Same goes for dynamic range, although that's often something you can control when shooting. Although it does give you more options and lowers the chance of burning highlights or having noisy shadows.