In photography, you often ask or get asked, what's better. This or that body or lens or some other piece of equipment. My opinion is almost always that it really depends on what you are going to be doing with it.
For example, there is a lot of debate as to what is better - full frame or cropped body. My answer is usually preceded with a question about what that person is going to be using it for. Some people will speak of "upgrading" to a full frame body when they are really very different tools. One doesn't upgrade from a hammer to a socket wrench. They are different tools and although there can be overlap, each one can have advantages over the other.
In the case of crop sensor cameras, I have thoroughly enjoyed my Canon 7D MkII even when shooting with it alongside my 1Dx and now my 1Dx MkII. As new bodies are developed and become affordable, many of us may be behind, technology-wise, since not all of us can afford to always have the latest and greatest that just came out. I know I don't have that luxury; my newest body now being four years old at the time of purchase.
So, what is better? Full frame or cropped body? The questions I ask are what will you be shooting, with what lenses, and under what circumstances? When I'm out shooting dark scenes such as live music, I always carry full frame bodies because I need to maximize my performance at much higher ISO values than normally encountered otherwise. I carry two bodies when I can so I don't have to switch lenses as often, something I can hardly afford when shooting fast action under a short time constraint. The image below was shot with a full frame Canon 6D at ISO 12,800.
And what's high to you is likely not high to me at all. Many will set their upper limit on their cameras to 1600. I see that as a total waste of great technology. You can read my blog post about shooting a crop body at 12,800 and decide for yourself.
Besides, what are you to do if the scene calls for a higher ISO? Do you just not shoot or do you just underexpose? I am going to keep shooting.
When I'm shooting wildlife, my needs change and so do my tools. I'm usually shooting from a tripod and at a higher shutter speed but I am usually shooting under a lot more light. My ISO values may still be somewhat high because of the slower aperture of supertelephoto lenses, often with teleconverters added to them, and the desire to stop action. But a scene at ISO 8000 outside and during the day is a lot more cooperative for suppressing noise than one in a dark concert arena.
For added reach, and when I have plenty of light, my go-to body is my cropped 7D MkII. While some complain about noisy results, I find that I can get beautiful images pretty consistently. Consider this image taken at ISO 1600 and f8 with a 2x teleconverter.
When shooting early in the morning, under heavily overcast skies, or in otherwise subdued light, my tool becomes the 1Dx or now the 1Dx MkII. I found that the older body we pretty comparable to the cropped 7D MkII at ISOs below 3200. But now with the newer MkII model, the ability to turn off the anti-aliasing filter improves my sharpness substantially. But even its performance has its limits as I shoot smaller and/or more distant subjects where the 1.6 crop factor becomes as advantage with the older 7D MkII. I believe the jury is still out about at what ISO the tradeoff becomes with the newer body. It may be that the sharpness gain and lower noise outweigh that 60% extra reach.
But for the more affordable full frame bodies like the 5D and 6D series, my experience shows that they are equal partners with the 7D MkII in the image quality department and the latter should be considered as a great companion for much general purpose and especially wildlife photography that many of us enjoy.