>>178199There are many differences to consider:
- A sensitive needle will be more responsive, and won't be demagnetized before a long time, though more prone to be affected by anomalies.
- A free moving needle mounted on a sapphire will more easily point at the north, while a chinese made one will scrape on its balance point, and despite the needle struggling to align with the north, it won't unless you shake it or gently tap on it, and even then it may just get stucked somewhere else.
- Some are liquid filled, some aren't. Liquid may froze at cold temperatures, so it's usually some kind of oil, that nonetheless impedes the needle movement unlike water would, and even more unlike air would. Some can also have, at high altitude, bubbles that form because the pressure is so high air gets in. Gas-filled compasses don't have most of those problems, and quality ones with quality sealing won't have any problem at all.
- The direction of Earth's magnetic field changes depending on the hemisphere you're in. Some can be rebalanced in the field to make up for that, others like Suuntos have global needles that will point at the north wherever you are. Many decent compasses are barely usable in the southern hemisphere because the needles will be pointing down, some are completely unusable.
Many other points could be mentioned, but yes, there can be a great difference.
Of course, it all depends on the use you have for a compass, and whether you just need to get a vague bearing, a more precise one, pinpoint your location, or some other more advanced uses. Most hikers just need a basic compass.
