If you are NOT trying to lose weight in that area then repetitions will build muscle. The difference in the way you do the exercises will show up differently on the body.
One time I was solid and pretty nicely muscled, not a body builder by any means though. I was seriously trying to make some areas smaller though. The weight trainer at the gym told me that I needed to stop doing so many repetitions because all I was doing was building muscles and there was a layer of fat between the muscles I was working on. He said I needed to lose weight first, let the muscles go for a while, then once the fat was less in that area I could start the repetitions again to tone and shape the arms and thighs.