See this interesting article by Michael Frye on Setting the White Point in Lightroom: A Comparison:

Since I advocate using the Point Curve in Lightroom to set a white point and black point, I sometimes get asked about the difference between doing this with the point curve, and doing it with the Blacks and Exposure sliders. The first part of the answer is that there is no difference—at least none that I can see—between using the Blacks slider and moving the lower-left end of the Point Curve to the right.

But there is a difference between using the Exposure slider to set a white point and doing it with the Point Curve. When Lightroom first came out Adobe said that pushing the Exposure slider to the right was the same as setting a white point with Levels or Curves in Photoshop, and everyone seems to have taken this as gospel. Maybe Adobe said that to justify not including Levels or a real point curve in early versions of Lightroom. But it’s not the same, and it’s easy to dispel that myth, especially now that Lightroom has a real point curve:

In my view this is partly a case of wanting to work Photoshop-style with the same levels and curves tools that you’ve used for years. In terms of time effectiveness (never forget Lightroom is about workflow efficiency), I doubt there’s any difference in setting the white and black points with the sliders or dragging the curve, so I’ll take that out of the equation. But the real danger I see in this approach is of neglecting the adaptive tools – Recovery and Fill Light – which only target contiguous areas of the brightest highlights or contiguous areas of shadow tones. So these tools protect the spectral highlights and the points of purest black. By forcing the point curve to perform all your clipping recovery, you are altering all the brightest tones in the image – what makes it sparkle. Is it coincidental that Frye uses a low contrast image without much shadow? Use the point curve when it’s needed, but why work with one hand tied behind your back?