I stopped registering songs with the USLOC copyright office years ago.
The fact is, no one is likely to steal your song. It's extremely hard to even get people to listen. There's also some 3rd party date of creation services such as Songuard which are much less costly if you really need to have a 3rd party vouch for you. Not counting the fact that all computer files are dated, and servers online record the dates you upload the file to it.... And my main reason for not using the LOC is that if you are an artist, your label should pick up that cost for you, and if you're a song writer as I am, the publisher who signs the song will pay to have it copyrighted in his company name.
So no, I don't use the LOC and I sleep well at night. I used to be paranoid about that stuff until I learn the things I just pointed out. However, if you have the money and wish to copyright everything so you can sleep better, by all means, disregard the preceding paragraph and continue to register your material with the USLOC.
I would register a copyright with the LOC IF I was going to release an album on my own. Beyond that, no.
So.. to answer the question. Neither.