I have had two children, both at small LACs. One had an all freshman dorm, the other was Vassar. I like Vassar’s system better, to my surprise. My Vassar child’s residence hall had 1st, 2nd, and 3rd year students living in it - the majority of 3rd years were living in singles, and some of the 2nd years. The 1st year students all lived in discrete sections of the halls where they were surrounded by other 1st year students. The upper-class students included residence hall “officers” who arranged social events and activities that all students in the residence hall participated in, though it seemed that many were more 1st years than anyone else. There was also a faculty family living in the residence hall.
Upshot is that the Vassar dorm was more socially “healthy” - upper-class students were there in the social rooms and spaces as mentors, friends, as people who could answer questions about Vassar, while there was still a strong freshman community in the dorm (the orientation groups were also the students living right next to each other, so there were multiple opportunities to get to know them).
The 1st year orientation worked very well to develop both a “residence hall” community, and a cross-campus class based community, so that my child’s friend group included some people that he lived with, and others that he did not.
I think people who have not been in a small LAC might underestimate how important cross-class friendships are in small schools, and Vassar facilitates this.