I'm guessing Jim is alluding to the "a copyright is only as strong as your ability (read money) to pursue it through the courts for several years" perspective, which is a viewpoint I have some sympathy with. That said, at ~$35 per registration with US copyright office, and as a registration can be a collection of songs, it need not be hugely expensive. That is certainly the only copyright service I would consider. To be honest, it also depends on if you plan to be a professional songwriter, what your immediate prospects are etc. as to whether realistically it is worth your while registering your songs, but that is down to the individual writers and their realistic prospects. Are many lawyers offering a "no-win-no-fee" for copyright cases? I doubt it. That said, if you are a member of musician's unions or some songwriting societies, many offer free legal services up to a certain cost... which is why, on balance, I think it is worth while.
Whether you plan to release your own version, or simply use a good recording to get established artists to record your song, then a pro standard recording is definitely needed. The days of sending off demo standard recordings has long passed. That said, "pro standard" doesn't necessarily mean complex, expansive, or expensive. It could be one voice and an accompanying instrument, although much depends if you are targetting specific genres of artists or the song is more genre specific than cross genre. Be aware, it is a very, very competitive market these days.