I'm having a similar issue w/ my three year old, Morgan. She'll go pee most of the time, but not poop. She will wear panties and she'll still go. Mostly she's preoccupied w/ playing and doesn't want to stop playing to go use the potty. The past couple of days I've just put her in pants w/ NO panties (not jeans, of course, that would feel funny!) and she's been really good. I think even w/ panties Morgan felt a sense of security, like something was there to catch it. But, she's been good.
Another thing we've done that has semi-helped is go at particular times. When she wakes in the morning and from her nap; before she goes to bed at night and before her nap; before dinner; any time we are JUST about to leave the house and then if she doesn't go at that time, we find the bathroom wherever we are and she goes when we get there (even at stores/restaurants). It's seemed to have helped for pee, but poop she's still resistant on.
GOOD LUCK! I'm right there with you! :)
Oh, and I have a near 2 year old, too. So, today I'm starting something new... Everytime my oldest goes on the potty, my youngest, Jordyn, will, too. My oldest will sit on the big potty (which she's fine doing) and my youngest will sit on the little on. Jordyn has already wanted to sit on it when Morgan's on it so I figured why not give it a shot!
And yes, what other women have said is very true... every child is different.
If you find a technique that works let me know! :)