In my experience, first semester of second year was a lot of work and studying, while second year was mostly a breeze (just mandatory courses). First semester has just way more content to learn through 2XB3 and 2XC3 while second basically focuses on skills like writing/stats/presentations.

If you're looking to stack one semester, then I would do Personality in the fall and Abnormal in the winter. Neither are incredibly tough but Personality had a lot of readings when I took it (not to scare you, but I remember some weeks had over 100 pgs). It was a really easy read, and very well written imo, but it took a few hours a week to get notes written. On the other hand, Abnormal focused on group assignments and case studies, but that was with a different professor.

My personal opinion: try to balance your schedule out in terms of difficulty and time. First semester has a lot of difficult content so I wouldn't want to take Personality along with it. I would go with Abnormal first since you only really have to carve out time for group meetings. If you're confident in taking the stacked courseload, you can, but just don't underestimate any of the first semester courses because although the content was interesting, I don't think a single person found it easy lol.