They are both sour. If you use too much of either one, the beer will have a distinctive tartness. My club did a brew a couple years ago where we had specified too much acidulated malt. The beer had no pellicle and did not become more tart over time. It was the acidulated. Fortunately, with either one, it's a mild mellow acidity, and if you don't overdo it, it tastes good.
So... use restraint, use just barely enough to hit your pH goal, and you'll be fine.