tl;dr: `innerHTML = '';` is faster.

Since last week @davidflanagan and I have been volleying a perf test to determine the best possible approach and David landed on the irrefutable evidence yesterday, which I then extended to get further evidence.

http://jsperf.com/child-removal-deathmatch/10
http://jsperf.com/child-removal-deathmatch/11


(I'll repost this comment to dev-gaia)