The best use of it is for those whites that have high malic like garymc stated. But you don't want to just use it as a standard culture for all whites. It's pretty impossible to use ANYTHING carte blanche. You need to know the characteristics of the grape or fruit you're using.
You sure would not want to use 71B on Niagara!!! It would make it taste like dishwater. Just because a fruit has malic on it doesn't mean you will want to reduce the malic. For example, we use 71B on Bartlett pear because the malic is so harsh in the resulting wine. But we don't use it on apple even tho it's a malic fruit because the acid on it does not come out harsh and you need that acid to add crispness. Peach is also malic and considered a white-style wine. But reducing the malic on that would result in more dishwater. Blackberry is VERY harsh and it's always desireable to reduce some of the malic to make a smoother wine. So don't just use it will-nilly. 71B is a desired culture when it has a PURPOSE. Design your wines by choosing the cultures that give you the desired result you're looking for.