Well where it starts, ends and all that noise is individual anyway. For my money, the difference is in the purpose:
RDL is used to groove an arched back pull where the prime mover is the hips/hams. The weight used isn't as high as for the SLDL because it's just a far stricter exercise.
SLDL is used to groove a round back where the lower back flexes as well. It's basically very similar to a full conventional deadlift.
Very different purpose and performance. I think if you do a sloppy RDL then it will end up looking like a partial SLDL and then in my opinion you've also completely missed the point. For me personally, I wouldn't say that video Steve posted is an RDL. Upper back rounds, it's a partial SLDL. For my money! So apart from it being a good feat of strength, I'd question the value in it. If you're rounding and flexing your back why not just take it all the way down? The RDL typically stops shy of the floor because of a nice arch in the back, shoulders back and tight locked (but slightly bent) legs. But if you're rounding your back and bending the legs to that degree anyway, why artificially stop the movement? Makes no sense to me.
But having said that arguing over semantics seems a bit silly really, especially in this. It's all about what you're doing the movement for, and knowing how it's going to assist you.
Last edited by Fazc; 03-13-2013 at 10:06 AM.