There is a vast difference in the academics (pace, expectations etc) between Hotchkiss and Salisbury. I have 3 sons; 2 went to Hotchkiss and the other one applied to Salisbury, and we seriously considered it for him. I am not as familiar with the other schools.
If your son struggled at all academically (and I know there could be a bunch of different reasons, none of which have to do with intelligence) I would think long and hard about Hotchkiss.