Trade in or sell privately?

Hello all, first thanks for all the replies to the Egas ute thread. 
Very informative and useful. Now I know what the issues are.

We have 3 cars a 99 318i BMW a 98 RAV4 5 door and a beat up old XF ute. 
All running well.

We plan on buying a Mazda 6 to replace the BMW and a cab chassis Ford 
ute to replace the RAV and the XF.

We will be paying cash for the new cars.

Should we sell privately of trade them in? What are thre pitfalls?

(I doubt the XF would get a roadworthy certificate as it is.)


Mekon