I like the look of chrome as long as they dont have Edelbrock, Moroso, or some other brand name on them. Aluminum covers seal better and will not distort when tightened down. The key though with either is to use decent gaskets. Moroso makes an EPDM gasket with a steel inner core that is superb. Use no glue/sealer on them though. That stuff has never stopped any leaks and causes big problems if you ever have to remove the cover. If you must use some to hold it to the cover, only use the minimum amount and put it on the cover only.