Are all water droplets created equal?

No, rain is water that has condensed in the atmosphere by way of the water particles bumping into each other and making the drops (mass) bigger. When it is big enough to be effected by gravity, it falls to earth, on the way down it may or may not bump into more water particles effecting the mass. How big a drop is depends on how many collisions it has on the way down.

It can also pick up impurities out of the air on the way down, ever notice how clean the air smells right after a rain?

No snowflake is alike another. Snowflakes come from raindrops. So to add on to the answer @DrBill gave: just think of snowflakes! :P

@morningmomo Snowflakes do not actually come from raindrops. Raindrops are formed by water vapor condensing into water droplets, will snowflakes are formed by water vapor condensing straight into ice. Sleet and freezing rain come from raindrops, though.

@PhiNotPi Well, I just learned something new :P (My snowflake comment still sorta-kinda fits in I guess). Thanks for letting me know!

Dr. Bill gave the best answer.

@Ltryptophan As @DrBill noted, not even every raindrop is the same. Far from it.

But I am pretty sure you would agree that a water droplet from my bladder is not created in the same equal way a water droplet of rain is created. And it isn’t the same as a typical raindrop when it emerges into the air. Case closed.