I transfer whatever I need to hit my desired fermenter volume. That's my main goal.
Depending on how my trub settles in the kettle and how careful I am with the siphon, sometimes that means a little gunkage makes it to the fermenter, sometimes a lot. In the finished beer, I cannot tell the difference one way or another. That may be a benefit to my small-batch brewing or it may be true in general. I don't know.
However, I'm willing to accept the science on this, if it exists.