A friend used the mini kegs before and even manged to rig up a CO2 charge system to one, but it couldn't handle much pressure. Only enough to serve with. Too much and the rubber bung would pop out.
The problem with the mini kegs is that once you tap them, you introduce air inside and the beer must be drank right away. The Homedraft system fills the airspace with CO2 and keeps the beer fresher longer, and also keeps it carbed.
$ for $ I think the homedraft system is the way to go if you can figure out which CO2 carts to use with it. The only downside is having to drink that American Light Lager first!