Better supplies will allow u to multi task, run 2 chargers, a lathe ect ect....
Also better supplies are longer lasting.
The best bang for the buck is the Pyramid PSV-200. ITs 20amps with a cooling fan. 50$US!! A bunch of us have them at my track and they sure blow away the overpriced much more units. I had retired my trusty 15amp pyramid of 10years for this new light weight job. Never had issues with the old pyramid...
We got ours from:
http://www.buyreliant.com/psupplies/psv200.htm