Will, the natives here gave excellent answers.
As a learner, I would add that once I figured out they are pronounced virtually the same, it mattered a lot less. As a westerner, I needed to put some time in to learn the 'flipped R', which appears in many languages but not english. It is like the hard double d in Ladder, you flap the tip of the tongue against the alveolar ridge. The D is only slightly removed from this, with the toungue moving down the back of your top teeth.
The main point is when spoken they are almost indistinguishable.