William, The Main Mt. Whitney Trail is 11 miles long, while the shorter North Fork Lone Pine Creek route (Mountaineers Route) is about half the distance. When you have to tramp through miles and miles of snow, a shorter distance makes good sense.
In addition, on the main trail, once past Trail Camp at 12,500, the trail is generally abandoned, and people will climb the steep slope west of the switchbacks (misnamed "the chute"). However NVG made his day hike on the main trail (February 19th Day Summit in the Trip Reports), using the switchbacks. More snow has fallen since then, so no one knows how deep it is now. And last, there is a short descent from Trail Crest down to the junction with the JMT (John Muir Trail) that can get a lot of drifted snow, much exposure, and might be treacherous to traverse if the snow makes a steep slope.
I don't like to say this, but March is not a good time for anyone without strong winter climbing experience to be hiking Whitney. For you, I would recommend joining a guided climbing service to climb in March. There are several outfits, and they all guide on the Mountaineers Route.
Good luck!! | 
