Is it worth backtesting on a couple years of data?
Definitely not.
Without backtesting a thing, I can tell from the underlying indices that the two funds should have very similar performance. They're both globally cap-weighted passive options, so most of the performance will be determined by the top few hundred companies that should be virtually identical in both funds.
If your goal is maximum diversification, I might personally be inclined to go with Option B simply because the 10% emerging market exposure will likely have a greater diversification effect than a few more smaller companies in developed countries. But IMO both are good options.