Final answer:
The main difference between a White Russian and a Black Russian is the use of cream. A White Russian includes cream while a Black Russian does not.
Step-by-step explanation:
The main difference between a White Russian and a Black Russian is the use of cream. A White Russian is made with vodka, coffee liqueur, and cream, while a Black Russian is made with vodka and coffee liqueur, but does not include any cream. The presence of cream in the White Russian gives it a smoother and creamier taste compared to the Black Russian.
The other options mentioned in the question - garnish with lime and type of glass used - are not differences between the two drinks. They are variations that can be added to either a White Russian or a Black Russian, depending on personal preference.