Copper vs. aluminum buss duct

We are adding onto our manufacturing facility.  One electrical design uses aluminum buss duct for 480V distribution.  Another uses copper buss duct.  Aside from price, what are they advantages and disadvantges of each?

Torqued aluminum connections can relax due to creep. That causes me concern. Even periodic retorquing may not be a good solution since it just accelerates the distortion of the components. I have seen some pretty distorted bus connection areas at our aluminum isophase bus connections where the washer causes an indentation into the adjacent bus section. I've never seen a failure yet but I don't like it.

The copper bus ducts are characterised by low resistivity and high weight, while the aluminum bus ducts are characterised by a bit higher resistivity and LOWER weight, considering the same cross section.

Usually the aluminum bus ducts are chosen when the mechanical load (weight) is a problem.

Suggestions:
1. It is convenient to have all copper or all aluminum buses since the transitions from copper to aluminum and vice-versa may pose some challenges. Also, connections to transformers and switchgear could pose some challenges if of dissimilar metal.
2. For the same load, the aluminum buses will be more voluminous.
3. Since the bus amp ratings are not posted, the availability of copper and aluminum buses of your required ratings should be checked.