Aluminum winding in inverters
The primary driver here is probably cost. Aluminium is cheaper then copper. 

For high-current windings, you need a lot of copper/aluminium. I'd imagine that by switching to aluminium, the manufacturers can save money in the transformer production expenses.

Regarding "longevity" and "efficiency":


Aluminium can be difficult to connect to, if connectors designed specifically for aluminium are not used.
Copper is a better conductor then aluminium, though this can be compensated for by simply using more and thicker aluminium. However, this will likely require the aluminium-wiring transformer to be physically larger.
This could lead to more leakage flux, rendering the transformer less efficient.




Realistically, the major factors in what makes a quality transformer are independent from the transformer winding material all together. You can have crappy copper transformers, or great aluminium transformers. 

Chose based on actual quality, warranty, etc....