I never used MYPD but have tought about this. Unless you have all these ingredients readily available, using wort seems to me the most economic solution for growing yeast.
But I’d be interested in the difference in yeast growth as well.
Don’t you though end up with the same problem as if you made starters with sugar water? That is, you may end up with more yeast, but they’ll be yeast with a taste for glucose and not so much for maltose.
I haven’t tested it, the plates and media I use for growth use YPD, which is only glucose, but that is only for growing 3 mls for freezing or as a first step after picking a colony from a plate. Everything else gets wort with nutrient added.
Doesn’t look like there’d be much difference between the MYPD and a wort with some Wyeast nutrient added. The malt extract part is identical obvisously, the nutrient has yeast extract, peptone is amino acids which boiled wort has, and the sugars are basically the same (maltose being a disaccharide of two glucose molecules, and yeast having an invertase enzyme).