Grabbing with the right trigger. My problem was that I don't use the joystick that much, so I'm not great at moving it exactly in a particular direction. So I'd often be moving sideways, but then drift slightly up or down into spikes or off the bottom since I wasn't holding the joystick exactly horizontally. I pretty much couldn't reliable move continuously, and had to nudge a bit, pause to see which way I drifted, then nudge again to correct the drift.
With the d-pad, on the other hand, it's easy to go exactly in a single direction.