Alt Az will track more or less as accurately as an equitorial, but you get very fast image rotation. If you want to image with an Alt Az you will either have to use an image de-rotator (another motor at the focusser, which then needs controlling accurately) or you would need a wedge so that the fork mount is 'pointing' at the north pole.

A second issue with an Alt Az and an image de-rotator is that it still can't image across the zenith... it has to rotate extremely fast as you go past the zenith. The real amateur solution is the wedge, but they're not free.

If you go for a german mount then it will expect to be polar aligned, again if it isn't perfect, then as you track you get image rotation, but only slight compared to an Alt Az, and if you image with lots of shorter images, say 10 minutes each, then slight rotation isn't usually an issue.

Can you tell I only have German mounts?

yours utterly biased :D

Derek