The parallel is the most versatile breakout board we have and will work with most of the software out there, but many computers are not equipped with parallel connectors anymore. Parallel adapter cards are available if you don't have a parallel connection on your computer.
The USB interface must be used only with the planet-cnc software, which is great software, but you are still limited to only that software application. This is actually the least expensive option unless you use linux and go with the above option.
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WHATISTHE DIFFERENCE WTIH THE PARALLEL BREAKOUT BOARD AND USB BOARD?