Aluminum vs. wood makes for an interesting discussion but pales in comparison to proper floor plan.
If the floor plan is right. If the cost is right. If the TT weight is not an excess burden to the tow vehicle; then the choice of wood vs. aluminum might come into consideration.
Wood rots, aluminum corrodes, both of which are signs of water leaks which may ruin everything around them, regardless of what they are made of.
The manufacturer chooses wood or aluminum base on the manufacturing methods needed to meet their target design and market price.