Whats the difference between an L and non L model? I know that the L is low voltage (115 vs 220) but what does this mean in terms of heat, power, etc?

I don't think there is any difference in manufacturer's specs. And I doubt there is any difference in actual performance.

If I were manufacturing the pumps, the motor windings would be built identically, and I would just make series or parallel connections between windings depending on whether the pump was to be for 220V or 110V.

Got KarmA,

From reading the above posts I'd guess you changed to the MD-20RZ, but it doesn't really say.

Which pump, and what can you tell us?

Well, I changed my order from the MD30RZ to the MD20RZ, but have not received the unit yet. Underwatercreations (a rave on their outstanding customer service once the iwaki hooligans is dealt with and sorted out will be coming ...) is jumping through hoops for me to get me the pump I want at the price I want .... so I'm giving them plenty of time to do it and am willing to swallow delays.

I'll give some comparisons between my Eheim 1060 and Iwaki MD20RZ when I get it.