Vests are so chic and will give an outfit a finished look. Your “leather like” fashion vest sounds very stylish and a good investment since you can wear vests open or closed to create many different looks. From your description “it looks good open” you can definitely wear it open. An open vest will probably look a little more casual. If it fits well zipped up and looks good with what you are wearing you can wear your vest that way also. Experiment with some different outfits for some different looks.