It's not particularly close. The WCC is significantly stronger.
By the way, your BPI article is 13 months old.
The WCC is the 8th strongest league this year. The MWC is the 11th strongest.
This is math. Saying the MWC is stronger this season is like being a flat earther. If you're not familiar with Net Rankings and Kenpom, I understand.
I get that CB is focused more on arena size than the on court quality, but the WCC has been trending up and the MWC has been trending down. The WCC's advantage in revenue, tv, and having the two most recognizable non Pac-12 basketball brands in the West has been, predictably, pushing the WCC forward. In the meantime, the MWC continues to have a lesser tv deal and minimal NCAA Tournament revenue.