If you were prepared to spend $3300 on a TV, the best TV for that price would be a Panasonic 65VT50, 65GT50 or Samsung 64E8000. That lesser model Samsung isn't really comparable to the specs of the 70" Sharp.
But yeah, that Sharp LED isn't bad but it certainly doesn't compare to the plasmas for that price. The plasmas blow it away with motion, color and black levels.
He probably said to get the LED because HHGregg doesn't sell the better Panasonic or Samsung plasmas. I checked their website and none of them came up. He works on commission and wants your sale, he's not looking to make the best recommendation for you, since he doesn't have the best TVs.
Do yourself a favor and go and read up on TV reviews on CNET or on here and buy a panasonic plasma from Best Buy or Amazon. Or at the very least do a little more research so if you do decide to stick with your original choice of a 70" Sharp, you can at least have more knowledge of your choices.
I used to sell these things daily, and that Sharp doesn't hold a candle to the VT50