I’d start in the fall if at all possible.
Leases in most college towns run in conjunction with a fall start and last one year. So find housing can be more difficult.
Most of the students are starting in the fall and making friends when no one really knows anyone else is easier.
For many majors, the best way is to belong to a study group (whether formal or informal) and being on the same track with others taking the exact same classes is important.
With fewer students starting in the spring, fewer classes may be available, negating your ideas about class size.
Some schools only admit new students in the fall.
I can’t think of any real positives for starting in the spring.