They are all improvements, though for me KA is the most exciting both in terms of enhanced earning/burning and because of their quality shorthaul product. MA gives access to some of the more esoteric bits of Europe, RJ will fill the gap left by the loss of BMed. JL is a bit less exciting, but does offer a good product to NRT and some extra connections to China/Korea.

Being utterly selfish, had AS been joining then I truly would have been unmoved.