This difference is that in any practical capacity if you are doing this you are almost 100% giving out trade secrets. It's almost impossible not to. Also, your analogy is wrong. It would be that you are a flooring company and one of your workers is working for both you and your competitor, and no doubt using any clever techniques or processes that you've come up with to help out your competitor.

The software industry is big enough that you can definitely find secondary employment at a company that isn't direct competitor. That you want to apparently game multiple parties for your own gain seems like a pretty terrible thing from the employer side of the fence.

Once the company I work for had an employee from a direct competitor apply for a job with us immediately after quitting. They were pretty forthcoming with offering us intel on the competitor, presumably within their contract. We still turned them down because if someone has that little respect for a working relationship with their previous employer you can be sure that they will do the same to you.

People here often like to paint the picture of the people versus evil corporations. In reality, a job is something where you should have mutual respect between employees and employers. To me and many others, this is part of being a professional.