I think they both go in totally different directions, really.

Estelle's only does [i]one thing[/i], and that's probably the only reason it can move around like it does, and it took her entire family working on that for a very long time to achieve.

Meanwhile, Mira's is crazy in its functionality but can't move, like every other bounded field around. I think Mira's is more impressive practically still but in terms of magecraft and all the Varianbec family achieved something pretty crazy.

... Aaaand now they're all gone and the only person who knows it is the vessel for the Redrock Grail.