As if selecting a chain to anchor your boat with wasn't complicated enough, there is one other variable that needs to be sorted out: Link length!
Both of these chains are 3/8 links. The chain on the left is 3/8 BBB while the chain on the right is 3/8 Mooring Link. BBB is calibrated to fit and run in a windlass gypsy, while Mooring LInk, sometimes abbreviated as MC for Mooring Chain, is not calibrated to run in a windlass.
What happens is, the regular links of BBB and other standard anchor chains are too close together to fit a shackle through the link in any place other than at the ends. This means that it is impossible to tie in another chain to a different anchor part way through the line. To help with moorings, MC chain has longer gaps in the link, allowing a shackle to fit in any point on the chain. This makes it especially easy to set up a Bahamian Mooring, where you have an anchor at either end of the chain, and hook your boats rode into the middle of the chain setup.
When you purchase chain, make sure it will run smoothly through your windlass if you need it to do that. And be careful because both of these chains are listed as 3/8", it all comes down to the link style.