Whichever one you like! But...the most "accurate" of the Picture Controls and the most useful for those trying to preserve the best possible JPEG data for later post processing tends to be Neutral, sometimes with a Contrast setting of -1. Why? Because it's easier to add contrast, saturation, vibrance, and color shifts to neutral data than it is to remove those things from already modified pixels. Neutral, especially with AdobeRGB set as the Color Space, will produce pretty drab-looking out-of-camera JPEGs, though, and many people don't like that.
Note: cameras starting with the D4s (D750, D810, D5500) also have a new Flat Picture Control, which takes out the delinearization curves used to make an image “usable.” I don’t recommend Flat for JPEG shooting because it puts too much information into the bottom four or five bits of the data set: when you try to make a better looking image in post processing, you’ll get rounding errors and posterization.
It's a pity that Nikon's engineers are stuck in the past. Most cameras have a bracket button, after all. In these days of advanced cameras, why we can't bracket anything, including Picture Controls, seems a bit archaic.
The act of photography is about making decisions, and "bracketing" is capturing multiple possible choices for delayed decision making. That Set Picture Control is buried in the SHOOTING menu of most advanced Nikons just adds insult to injury. Funny thing is that on my Panasonic LX-5 I press one button and I'm immediately on the Panasonic equivalent of Picture Controls.
But enough of the design lecture, let's get back to the question: one of the Picture Controls is likely to appeal to you more as the base for your image look. Experiment finding the right base first (Standard, Neutral, Vivid, etc.), then experiment with the parameters within the Picture Control (Contrast, Hue, Saturation, etc.). Don't get stuck on the notion that one Picture Control will suffice for all your shooting needs. You might like a different base for portrait work than for landscape work, for instance. That means it'll take you awhile to find the proper Picture Control. Remember to save your changed Picture Controls (both on the camera and to a small settings card you carry with you).