Pros: comfort. adjustable, stretching straps let you breathe. You can get colors that don't make you look like you're running the neighborhood with a flak jacket. Sand for the bags is cheap and pretty easy. Cons: four floppy velcro straps are a little trickier to deal with than another vest I have, but I can't breathe as well in that two-strap other vest. Don't leave it in your trunk where air can't circulate around it after use- little smelly, but that goes away after air gets around it for a little while. The amount of lead shot it'd take to get this vest to 30 pounds would cost between 60 and 100 bucks, depending on the hysterics of the market, but 20 lbs of sand is fine for my runs. There ya go. I like this vest, and I've recommended it to others I work out with.