The difference is the science backing all of the latter is far more sound than the big bang.
Light speed travel we will never know until we reach lght speed, which isn't happeneing anytime soon.
How do you suppose we test the big bang out?
Its a theory and an educated guess. There is ZERO modern day evidence to support it. Its just as likely God crated us as a bunch of particles developing into a single cell organism then evolved into dinosaurs and humans.
They are both unprovable