Can't get a smooth mouse pointer

I have really struggled with my new iMac because I simply cannot get a smooth / accurate mouse pointer. I have tried both a generic Microsoft mouse and a Logitech G400 and find that the pointer wiggles around and behaves as if it has dirt on the sensor.

However, when I had Windows 7 running via Bootcamp, both mice worked -very- smoothly.

I do a lot of precise Photoshop work and really struggle to get smooth accurate curves on the iMac because of this. I know that many factors come to play here, but has anyone else experienced this?

Both mice are wired and new.

Have you tweaked your System Preferences > Mouse

The Mac has been used by creatives for over 2 decades, demanding pixel perfection, if you're not getting that then there's something wrong. Personal, I have an Apple Trackpad, Mouse and Bamboo Tablet all plugged and going, swapping as needed and they all give excellent precision.

Yes - I have tweaked the system mouse preferences to find the most comfortable setting. I have wondered if maybe the mouse I use has too high a sample rate for the Mac - I did a bit of research and people suggested setting it to 125Hz. Need to find a way to changing the sample rate.