Will a cheap one hurt? Doubtful. But most real cheap CC's use a ball of steel mesh they shove into the main tank, and it's a PITA to clean. Versus a BT, or others that keep the mesh separate to make it easier to clean.
I'd save up and buy a BT, and keep it for years. But if money's tight, you could get by just fine with the eBay one, but it likely won't hold up as well as a quality unit.
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