Not even sure you'd get a "benefit" from the Beats component through the headphone jack, though there may be some with specific output devices.
The HP Beats setup is comprised of 2 things .. the specific layout and components of the built-in speaker system .. and a corresponding DSP to maximize the potential of those .. so they really are focused on the internal sound. Once you plug something into the headphone jack, you're using the DSP controls of the audio chip set .. which were optimized for the speakers. They probably work like most audio output devices and probably have more granular controls built-in, but it's still not an optimal way to use a laptop for DJing ... the main reason is there is no secondary output to cue music.
With a USB soundcard (and there are lots of options there), you can run the main outputs through a typically better grade of D/A converters and use the headphone jack to monitor the cue bus. OR, you can get a 4 channel USB soundcard and run decks 1 and 2 to separate channels on the mixer and have even greater control.
So I might use the headphone output for simple background music playing (and I have), but would always use a USB device for any real DJ work to get the best sound.