Vantage and poast plus are basically the same thing. Vantage is just the Whitetail Institute's name branding for it. Poast Plus has an oil additive that helps it stick to the leaves better. Neither should hurt your plot but the plus may burn the plot a little easier before it bounces back.

I have never used either but did a lot of research before deciding to not use anything that said you should not allow grazing for so many days after spraying.