I actually work for Korkers and thought I'd help out with the question as well.
dwtalso is correct, the Chrome is a more heavy duty upper material and has an added layer of sprayed on rubber toe protection. The BOA system is nearly identical , except the lacing guides are a bit more low profile and are welded on the Chromes. The Metalheads use BOA's traditional lacing guides which are a bit more open for extra drainage. The Metalheads have a few extra seams as well. They do fit nearly identical. For many folks , the Metalhead is a great all around boot, but if you need something a bit beefier or are just really tough on footwear, the Chrome is a great way to go. You can always give us a shout at the office as well if you have any questions about our products. All our contact info is on Korkers.com
Hopefully this was a bit helpful.