I've owned both, I still own the Legacy, the Precise is great, durable, all around great.
What is different? The button is a little different, both are good though. The Legacy is a little bigger, but also allows for the add on of an extention to use an 18650 with a Kick, you can do the same with the P+ with the Kicklet.
The price is the biggest difference for me, the Legacy is right around $100 for the Legacy + extention, the P+ and Kicklet are about $230.