Get the harbor freight unit (but be sure to use silicone caulk when you assemble it).
For big jobs, just get a portable unit, and use it in your yard or driveway. You lose the blast media that way, but realistically, how many big jobs will you be doing per year?
Make sure to put wheels on your blast cabinet when constructing it. Trust me, you'll be glad you did.
The total cost of the HF unit plus the portable unit will be about the cost of the 50 gallon drum cabinet you linked to.
G.