Cartridge Loading

I do not want to spend time trying to determine if 400 ohms sound better than 600 ohms

Then you will never know - because nobody else can tell you.

In addition to the factors mentioned by Newbee, the technically optimum loading for any LOMC depends on all the other components in the system, including the room. Anyone who tells you they know a LOMC's ideal impedance only knows it for their setup. Whether the same setting would be ideal in yours is anyone's guess.

If plug-n-play better suits your style, I'd suggest sticking to MM's. You'll save both money and time. LOMC's not only cost more, they take more work if you care about sound (and I assume you do, else you wouldn't have asked).

Sorry if that's not the answer you were hoping for - but IME it's the answer that's true.

Agree with Audiofeil. ;-)

Still, most MM/MI carts will perform satisfactorily (if not perfectly) into most MM phono stages at a standard 47k impedance, as Syntax said. You can't make that kind of blanket statement about MC's. That was really my only point.