Ings on the whole has been pretty disappointing - clearly this assessment is partly clouded by his injuries. But over the course of the season, he's looked increasingly off the pace. Yes he's linked up well on occasions but is rarely getting into goal-scoring positions (though both may be a function of playing deeper).
With Long, you'll get a 6 or 7/10 performance every week. His game is limited but he rarely goes missing -he'll occupy CBs, get us further up the pitch and create space for our better ball plays. That said, neither Ings nor Long is a long-term option.