It’s not so much they regretted the schools but their focus on wanting small schools and not wanting to look at big schools. They were young, they’d been to 3 different hs (small, medium, and large) and some other things were going thru their minds.
One is never happy with any decision but she did like her school, met her husband there, has many friends from college (her wedding only had 17 invited guests outside family and at least 10 were from college). But she’ll always want more, bigger, more well known. The other knew every one of those 10K students at her school, all her professors, returned for 2.5 years of grad school and still works (remotely) for some professors.
But so does a high school and we’ve read on here many times that a student who had 500 in their hs class doesn’t want to go to the state flagship because it will be HS 2.0. I went to a high school with 1000 in my graduating class, I hardly knew any of them (transferred in as a senior) and yet when I went to the flagship with 18k students I did run into a few. My nephew went to the same flagship 40 years later after graduating with 230 in his class and was still the best of friends with about 25 from his hs.
Pick the school you want. If you like big, go big. Neither situation is going to be perfect.