I am an Engineer for Unistrut and would be glad to help. If cost is a concern and is keeping you from using stainless, you may want to consider hot dipped galvanized. Cost is higher than the Pre Galvanized or Green, but corrosion resistance is much better. We do, however, use the green and pre galvanized a lot even for outdoor applications. They are the most economically priced and perform well in the weather still.
I am not a big fan of the gold personally, others may or may not disagree. The pre galvanized and green are pretty similar to each other in corrosion resistance.
If you have any other questions, do not hesitate to call me at our office 440-348-9450. My name is Matt.