My general thought on it has been that fluid observed before ejaculation is almost always pre-ejaculate fluid; sperm and semen generally requires the pumping action of orgasm in order to eject it through the various ducts and into and out of the urethra, whereas pre-ejaculate fluid is secreted directly into the urethra and doesn't require any such mechanism. I have observed that the pre-ejaculate fluid and seminal fluid have a similar taste and consistency.