Canon, followed by Nikon, are the market leaders. They have the largest development teams and overall the biggest amount of Knowhow, also in the details. A Canon or Nikon will usually produce great image quality etc right out of camera, without having to fiddle with raw software, and have pretty good ergonomics etc as well; they will get the job done, and usually very efficiently. However, their cameras are also a bit "boring" and "conventional", and they are slow to pick up on newer features like 4K Video.
Both Canon and Nikon have pretty good lens parks for full frame. Their APS-C offerings however are less great; for example Canon offers a good affordable wide angle zoom EF-S 10-18 f/4.5-5.6 IS for about 300$, but Nikons wide angle offerings for APS-C are awful, at least twice as expensive than the aforementioned lens and qualitywise disappointing. Still both companies in general offer very good quality and only have few stinkers among their offerings, the bad lenses are often the old ones that cant keep up with the ever crazier getting resolutions. Still a lot of the old glas keeps up surprisingly well; some of the really old lenses are still bitingly sharp even on 36 or 50 Megapixel sensors; examples for that include the
Nikon AI-S 80-200mm f4.5 N zoom or the Nikon AF 55mm f2.8 micro prime lens (Nikon lenses are called "Nikkor" but for reduced confusion I usually write Nikon instead).
Samsung is a newcomer in the photography market and a huge company that does all sorts of things. Just like with Sony, photography thus is only one thing among many they do. Thats why their cameras, just like those from Sony, dont appear being made from photographers.
Unlike Nikon and Canon who are kind of operating exclusively in this field; Nikon does all kinds of optics in general as well and Canon on top of that also does printers.
Samsung is officially extremely ambitious in their cameras, include all kinds of newest tech and in some models they include a lot of smartphone technology as well. However, they massively lack in the aforementioned Knowhow department, and thus their cameras are riddled with oddities. For example they made extremely ambitious claims about their cameras autofocus, saying they wanted the best of them all (a goal thats probably right now unarchievable with mirrorless cameras, though some other companies had quite some breakthroughs in this respect) but ended up with a camera that wouldnt find focus in the dark at all, just endlessly moving the focus around without ever locking on - LOL ! Its possible they have fixed that now, though. Still it was funny back then.
One says lenses are the most important part of any camera. There are also surprinsingly few tests about Samsung lenses, and there arent that many choices to being with, and the available choices are a bit odd and impractical, and the test results of them are not exciting either; for example the
Superzoom Samsung NX 18-200mm f/3.5-6.3 ED OIS iFn basically has no image quality worth mentioning and is possibly the worst lens I ever read a test about.
All in all, if you want special features of the Samsung, such as 4K Video or smartphone functionality, sure you can go for it, but - the best bang for the buck ? Nah, for that I think Nikon and Canon entry level DSLRs are unbeatable.