It all depends on several factors, how much do you weigh currently Legend? 10-20 pounds is nothing if you are a larger guy. To get any benefit from it you'd need to wear it all the time, so you have to take into consideration the weather in your area. If its hot most of the time, the vest will sweat you to death, as most are of dark color.
I used ankle and wrist weights to help lose weight, they also help in strengthening the legs. (I never got larger than 5 pound wrist weights just for the fact that if you walk with them they slide off of you, so the effect on the arms was less great.)
Gold's Gym has a very nice 40 pound vest. I suggest combining ankle with the vest though.