Photographers tend to be technical, and we talk about image quality a lot. It's something that's easy to quantify, superficially at least, and it gives us something to pursue. But it's not the most important thing about a camera – there are other important questions to think about first.
Can you afford it? Be realistic and remember that there are a lot of other important things in life, like memory cards and batteries and bags and tripods. Choose the budget level that’s comfortable and don’t worry about what anyone else is doing. There’s always something out there with more firepower – trust me, I once tried to justify a Better Light scanning back.
Can you use it? Cameras are biased toward right-handed and right-eyed people with excellent vision, mobility, and dexterity. That’s surprisingly few people. Grip shape, weight, button placement, eye relief, viewfinder style, and effectiveness of image stabilization are all things that nobody else can evaluate for you.
Will you carry it? The best camera in the world doesn't do much good if it’s sitting at home instead of being where you need it. A camera that can be carried in a pocket is fundamentally different from one that needs a dedicated carrying system, and a small bag is not the same as a large one. Remember also the extra weight and bulk of interchangeable lenses, if it takes them, and that everything is heavier at the end of the day.
Will it take the photos you want? The latest magic-camera won't help if it doesn’t suit your purpose. Mirrorless camera systems don’t yet offer a lot of macro lenses, and one with a substantial shutter lag will be a challenge at the velodrome. Image quality on the performance margins may start to be a factor here, but this question is much broader than just high-iso noise or dynamic range.
Do you like it? A camera that feels right will be easier to use. A camera that 'speaks to you' in some way will be used more often and with more enthusiasm; tactile quality and materials may make an unexpected difference. Some people gravitate to certain formats and styles of cameras, or even certain models in a brand. Don’t fight against irrationality here. Even colour and other aesthetic matters matter.
Who else has one? Communities make a difference. If three people in your closest circle use a particular camera system then you should need a fairly compelling reason to choose something outside of it. And the support for the biggest brands is exponentially greater than for the minor ones – not necessarily from the makers, who are often indifferent to the point of negligence, but from camera stores and photography instructors. As I write this a large store in New York has 243 different lenses in stock for Nikon cameras, 239 for Canon, 89 for Pentax, and twenty for Sigma SA mount. I like the Foveon sensor as much as anyone, but choosing something uncommon has complications. Only you can decide how much this matters, but sometimes it can be a very big deal.
Of course none of this means that image quality isn't important at all. "Is it satisfying" may well be my next question to consider, and how each factor is weighted will change under different circumstances. But image quality doesn't deserve the disproportionate attention that it takes up in our discussions or our efforts.