Perhaps it's due to which is your dominant hand?
Then again, it might just be a subjective/occasional perception, and not actually an actual fact.
You'd have to try a few different variations over a fair number of shaves to establish this obsevation's validity, I'd think. Such as a shave every 24 hours (keeping to a very similar diet and activity routine over the entire course of the observation period), and alternating which side is boar, and which is badger for each shave. Of course you have too make sure that the other variables vary as little as possible too - same brushes, soap/cream and razor/blades for each shave etc... and such stuff.