Who cares about statistics in 2015–2016 when making a debate about the current MVP award. The year is completely different.
As for actually debates about this year’s award, Westbrook is simply better in most traditional statistical categories and in most advanced stats as well. He has better PER, RPM, Wins, and has better on/off splits (by a huge margin compared to Harden). Harden really simply leads in certain efficiency numbers (mainly TS%) while Westbrook actually leads in other efficiency numbers like assist%, Rebound %, and assist to turnover rates. Where Harden has the lead besides shooting efficiency is team wins, but should that be all that matters? If so a player from GSW or the Spurs should win it every year.
Further, just like a triple double is somewhat of an arbitrary number for many people, so is 50 wins. Michael Jordan put up one of the best statical seasons in 88 and won MVP, he was soundly bounced in round 2. That season he won 50 games on the dot. If the bulls won 49, or 48 should jordan not have won the award?
The case for Westbrook is actually pretty easy. His team is a good team, he is putting up the best advanced numbers in the league (especially the numbers we have recently promoted as the stats we should look at for MVP like PER and splits), and he is doing something that we haven't seen in 50 years…even if it is arbitrary, it doesnt make it any less spectacular.