I recommend using Japanese rice vinegar to season your sushi rice.
Why I don't use white vinegar
White vinegar has a lot of acid and is very strong or sharp in taste.
With the wide availability of Japanese vinegar there really is no need to use it.
The Japanese variety (fermented rice) is very mellow tasting and best suited for your sushi rice.
It is usually mixed with salt and sugar to make the vinegared rice mixture used in your sushi. Some recipes even throw in sake (I don't). Here is my simple recipe: