The biggest factor is usually the lens ecosystem, not the camera body. Bodies come and go, but lenses are the long-term investment, so start by looking at what lenses you need now and may want later.

If you already own lenses in a given mount, staying with that system often makes the most sense so you can keep using them.

If you’re starting from scratch, compare each brand’s lens lineup and accessory ecosystem before choosing a body. Also consider what photographers around you use: sharing or borrowing lenses, flashes, and other accessories can be a real practical advantage.

Another consideration is backward compatibility. Some systems, notably Nikon and Pentax, have broad compatibility with many older lenses, which can be appealing if you want to buy used gear economically. The tradeoff is that older lenses may be manual focus and may offer limited metering or automation on some bodies.

So, choose the system based on lenses, compatibility, and the support network around you—not just the body specs.