Both are great choices for pre-med. You can major in anything and still get into medical school. Small LACs are really good for getting to know your professors (and hence good letters of recc).
You’ll also need to think about volunteer and clinical hours. The best way to do that is via a local hospital or physician. Looking at the maps, it looks like Colby has a small community hospital within walking distance of campus. Hamilton, on the other hand, the nearest hospital is about 20 mins away by car. Keep this in mind, as racking up clinical hours can take a long time.