Looking for a double jogging stroller...fixed front wheel or swivel? Which is better?

I am looking for a double jogging stroller for my 2 and half year old, and my 11 month old. We walk everyday, but I only have a single stroller and my son sits in that, while my daughter is wearing a harness and leash. Losing some left over baby weight is difficult when walking at the pace of a "stop and inspect every rock, pebble, stick, and puddle" curious toddler. :) I have heard that some prefer the swivel wheel over the fixed....mainly because it is easier to turn. Does a fixed wheel ride smoother? I live in a small town and there's often a sidewalk in front of three houses and then gr or gravel in front of the next five--especially on side streets. Also, some streets have rough patches and I'm worried the swivel wheeled stroller will be a pain on those areas, and cracked sidewalks. My sister recommends the swivel--but she lives near parks with paved paths for joggers. What say you?