What makes Alice different from Marisa?

In all likelihood of Alice having been intended to take the role of 'youkai Marisa' all across the series until Marisa retires from incident solving and transforms. They also obviously had different upbringings.

Marisa becoming a magician to defy her father's expectations. We can't say the same about Alice and Shinki. Actually we can't say Alice having had motives to surpass Makai's residents since her migrating to Gensokyo and not speaking two words to Yuuka whom I don't recall seeing after PoFV beats the point of that.

And there's a bit of interviews then and there about Alice explaining a bit on herself which I don't quite remember. If any of you having Headcanons regarding 'Alice and Marisa' differences then by all means.