I believe that they all fall into one of two schools: "Book 6", and "WBH". First In might be its own creation, but that probably means it has more up-to-date equations also used in WBH, plus extra detail.
Your needs dictate your likely choices.
For astrophysicists, no in-print edition will do.
For those who love detail, First In is probably the way to go.
For those who want something simpler or a modernized Book-6 version, Traveller5 will do.
For those who just need anything, then a half-page home-brewed system will work.