Reviving this question! #468 in 1001 in Orgo Chem Examkrackers says that Br- is a better nucleophile than Cl-, but #458 says that Br- is a better leaving group than Cl-. I get that Br- is bigger than Cl- and can therefore better stabilize the negative charge, making it a better leaving group. But wouldn't that also make it a worse nucleophile, because it can stabilize the negative charge better than Cl- and therefore has less reason than Cl- to react as a nucleophile?
How can something be both a better nucleophile AND a better leaving group?