My phantom 3 4K doesn’t hover very well even if there is a strong GPS signal. If there’s a light wind it’ll drift maybe a foot while it tries to maintain its spot.  In the same conditions, the Mavic's hover is rock solid.

Is this just old technology that’s not going to perform as well as the Mavic, or do you think there something wrong with the P3 4K

Also, this happens once but not again. The P3 4K has dropped in and out of that ATTI mode while flying.  Again In the same conditions, the Mavic was perfect. Since that happened I have updated all the software and Apps.

Thanks for your help

I suspect that there is nothing wrong with your P3 4K. It is just being outperformed by the Mavic's more sophisticated technology !  

A foot is not very much, but you could do an imu calibration to see if it helps.

As ALABAMA mentioned, you can do an IMU calibration and you can also check the props, make sure they are flawless.

You also have concider the degree of accuracy between the new mavic and your p3 one foot is most likely within its tolerance range.
I may be wrong about this because ive never owned a p3 but its just a thought that may be possible