Murasaki is very cute.
Are the varieties easier to grow than the type species?
do you get volunteer sowing around? not me.
are the seeds collected by the ants? 2 years in a row that I miss them.
I have to point out Véronique that I wrote ex. Murasaki for the fragrant seedling (it is not the true H. japonica Murasaki Choui). I didn't grow many H. japonica cultivars from seeds but I see that only few seedlings will come true to the mother plant. In any case, one will obtain seedlings with nice variations and can retain the best looking.
I suspect hybrids could be more vigorous than the species, but then it probably depends what species you are referring to.
Yes, the ants will carry away the seeds very fast when ripen. You should read through the Hepatica threads from a few years back, besides stunning pictures, there is a lot to learn.