The tough thing about COPYRIGHT and REGISTRATION is that it's protection is minimal. It's still a CIVIL lawsuit, not a CRIMINAL one. That means the burden of all proof remains with the plaintiff (person filing suit). The various registrations will do nothing but establish a non-partisan proof of date, but if someone "steals" an idea, you still have to prove they stole it intentionally in a court of law. The WGA Writer's Guild of America has one major flaw in that it's registration heavily favors it's union dues paying members. So if you try to sue a WGA writer using the WGA registration, they will be of very little help unless you are also a WGA member, then they can arbitrate otherwise, they tend to favor the WGA writer.
Similarly, the U.S. Copyright office and library of Congress tend to be useless in cases of copyright infringement because all they can do is provide a date you registered your work, which has nothing directly to do with the alleged "theft".
I personally find most forms of registration to be near-worthless, at least in my lawsuits regarding intellectual property theft - of which I have been involved in 2, both with studios and they never even saw a courtroom or filing, so I felt like registration is worthless to me.