What Type Fencing To Install?

I'm going to be having a fence installed sometime soon, and am curious to know the advantages/disadvantages of the wrought iron, aluminum, and composite types.
We live in Charlotte, and are told that the composite would be OK, but not to get black, as it will absorb too much heat and warp over time. White composite would work better, if we want to go that route.
I've seen both aluminum and wrought iron fencing at Lowe's as well, and wondering if the only advantage of the wrought iron over aluminum is strength, or if there are other advantages as well? The aluminum looks to be significantly less expensive than iron, and I won't be keeping a pet rhino in the fence...only a black lab.
Any advice out there?
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