These hold up really well for me, the one or two handled version, I like the synthetic better than the leather for some reason, but the dogs don't care which. They'll tug on anything and like it. I don't use balls on a string much anymore, they're too dangerous for me
A tug is a more stable target, if they launch to get the ball and they don't get it exactly, it usually moves around quite a bit swinging around by the rope which makes everything a target in the near vicinity, parts of myself included.
http://leerburg.com/minitug.htm
I've used a lot of other tugs over the years and most don't last that long. Some of the other fluffy type tugs they've ripped in half with one tug so I don't even waste my money on them anymore.