Wicker furniture gets its strength from the interlocking woven pattern that creates a tight web of support. The natural look also helps it blend with the outdoors. Cast aluminum doesn't rust and is very durable. It also looks really nice with cushions. In addition to this, you can match the overall climate and culture with the cushions as well. Cast aluminum can last a very long time and it is also a very light weight material.
When comparing both of these pieces of outdoor furniture, it generally comes down to pricing, as well as the buyer's taste. Modern outdoor wicker furniture provides more of a natural look that gives off a rustic or tropical feel. Cast aluminum has a little more versatility. The cushions can be changed to match the seasons or occasions. If you were to use cast aluminum for an event like a wedding, they would be easy to transport and stack. They offer more of an easy set up can help save money on transportation. Modern outdoor wicker furniture pretty much delivers the same convenience.
So will it be wicker furniture or cast aluminum? It pretty much comes down to personal preference.