You do realise we can prescribe whatever dose we like, right? Some drugs I prescribe in grams, some in milligrams and some in micrograms. The strength of a drug is somewhat irrelevant. I'm not going to prescribe a new and expensive drug just because the dose is 150mg when it's well-established, cheap cousin is available that happens to need a dose of 300mg.

It certainly is the context, and I believe it's what OP asked. If it wasn't, it should be, because it's the only question that really matters to me as the prescriber.

If what you're saying about the different pharmacodynamics is true (and this is actually what I'm talking about. I only mentioned milder effect because that seemed to be the difference in pharmacodynamics you were getting at), then this is an important difference. It would still have to somehow be quite different to the effect of the racemic version at any arbitrary dose to be preferentially prescribed.