Most stepper motors are very much the same, but at the same time they can be very, very different.
Different length motors will usually have different torque ratings. Generally, the higher the torque, the longer the motor.
You can get different motors with the same torque rating, that wuill perform differently. The difference is the current and inductance ratings. Higher current, lower inductance motors will have more torque at higher speeds than low current, high inductance motors. While they may cost the same, you may find that higher current motors need more expensive drives to deliver the higher current.
Most people here use Chinese motors, which are probably all very similar quality wise. If you want a better brand motor, look at Oriental motors or the made in the USA motors that Gecko sells. Expect to pay 50%-100% more for these higher quality motors. They may be a little more accurate, but don't expect to really see any performance improvements.