Work out your criteria before you look at companies, not after. Decide when you want to go, how long you've got, whether you're sailing or flying, what wildlife or landscape matters most, and which activities you'd be disappointed to miss. Then find the operator whose product fits. Doing it the other way round, picking a brand first and fitting your trip to it, is how people end up on a ship that was never right for them.
The distinction that does most of the work is expedition-leaning versus luxury-leaning. Every ship has a DNA. Some are built around getting you off the vessel as much as possible, with a big guide team and a serious activity programme. Others are built around the onboard experience, with better cabins, better food and a gentler pace. Both are legitimate. Booking the wrong one for your temperament is the mistake.
Ships that look near identical on a spec sheet can feel completely different once you're aboard, because the operator's style rather than the hull decides the atmosphere.