I own a Pulsar AS 150.?
On comparison 10w are thinner than 20w. And mostly 10w benefits where cold-starting temperatures are much lower, and therefore a thinner oil will do a better job of getting around the engine when it's cold. When at running temperature there will be no difference, as both oils are w50 and therefore they have same viscosity when at running temp. So in most of the Bikes in India comes with a recommendation to use 20w , so you shouldn't be worried as much but still be a bit conscious that you may find leakage in your engine here and there, so keep a regular check up of the oil level it might go down because of the leakage.