I just did the same thing Saturday. I tried on jeans and they fit in the waist and hips but were a tad baggy in the thighs. I tried the size down and I could get them on (they made my butt and thighs look awesome!) but were tight in the tummy and created a massive muffin top!
I went ahead and opted for the smaller size and hope to fit comfortably in 10-15 lbs since I could button, zip and squat in them - my dressing room test.