Standardized: Measured in a standard way, as in 15x of one standardized brand is the same strength as 15x of another standardized brand.

Non Standardized: They say this is 15x. It could be 10, it could be 1000, they just slap a number on it (typically they are slightly less than standardized equivelants.)

Honestly I don't know what the "standardized" way to measure is, and I doubt there is anyone verifying that anything is "standardized" in anyway. I would go for a higher strength non-standardized, it will probably be cheaper that way so you can get more.