"Maybe, but they're still both false! What exactly is the distinction you have in mind?"

Yes, and me and the Pacific Ocean are both more than 50% water by mass. Newtonian gravitation successfully explained a huge number of phenomena. Phlogiston did not.

"Anyway, I had just meant LET versus SR, but what exactly is the experimental evidence against an aether?"

With quantum mechanics (and modern experimental technology), we can actually look down below the level of individual particles, and we have found that photons are actually their own particles, not patterns of vibration (or whatever) within other particles.

"This would be a lot more convincing if the most recent and most successful theory of physics weren't such a glaring counter-example."

You mean quantum mechanics? Quantum mechanics is very elegant, it's just usually explained badly. See http://www.amazon.com/QED-Strange-Theory-Light-Matter/dp/0691024170.

"I disagree. Even under the naive theory of truth that is popular here"

Would you care to propose some alternative theory of truth?

"While that is still an open question people might come to different conclusions about which way is most promising."

Obviously, but that disagreement should then be resolved by reference to experiment. There is no room for persistent disagreement. In engineering, you can have five different methods, each with their own advantages and disadvantages, and this is a stable state. In science, having five different theories is not a stable state; it needs to be resolved, rather than harden into different factions.

"And then once you notice that theories of physics have this nasty habit of turning out false... well then I don't even know what you're using to declare A right and B wrong."

Experimental evidence?

"it then makes a lot of sense to think about the benefits working under different sets of theoretical assumptions (i.e. approaches)."

What does that even mean? How would you apply that to a theory of physics (past or present)? What "theoretical assumptions" are involved in, say, Special Relativity? Special Relativity makes the assertion that the speed of light is constant regardless of reference frame, but this isn't just a mathematical axiom that you can pick up and discard at will; it is based on a huge pile of experimental evidence.