I think that's mostly because of the proportions. If you take a look at Frodo here you can see the proportions I think mr. McBride uses when drawing halflings. Stomach Now Frodo here gets lots of exercise from tramping about and dropping rings in craters, so he didn't get a change to develop much of a belly. Most adventuring halflings, even though they still enjoy a good meal when resting at an inn, don't get the opportunity to grow big bellies.
Some people insist that halflings have pointy ears.
I have to disagree with that. Giving them pointy ears gives them a fey-ish look that I think is inappropriate for halflings. It doesn't work well with their build. Not that there's anything wrong with kender, but they just aren't halflings. Although halflings are a rather 'hairy' folk, they grow no facial hair.