For a definition of "efficient" that isn't shared by anyone else. This isn't a new rationale either, but a well known trade-off involved with JIT compilation and garbage collection. It's the reason Chrome "hogs" memory and Firefox is perceived as slow: they make different resource usage tradeoffs.
It will be interesting to see if the current memory crunch will impact this calculus going forward.
Firefox uses more memory than chrome in all my tests when I was using it for VNC (x11).