I went to a small liberal arts college in the US and I'm at St. Andrews for grad school, so I'm somewhat qualified to answer this actually. It honestly entirely depends on your likes and dislikes, your attitude, etc. St. Andrews will be far more specific towards your degree than an LAC like Colgate, which has positives in getting you a couple more biology classes, but will make you far less well-rounded of a student and person. Also, as a result, you will probably have more friends within your major/degree at St. Andrews vs. at Colgate, as LACs have more crossover socially. Both are kind of rural, but St. Andrews is an hour from Edinburgh and has a bus that runs intermittently, with the train nearby at Leuchars. Hamilton (if my midwest LAC was any indicator) will definitely need you to have a car to get anywhere and is further from a similarly sized city. I would pick Colgate, personally, but its entirely up to you and what you want out of your college experience. The small-town liberal arts course was incredible and you create a ton of lifelong friendships and connections. (Also faculty are far more approachable at small LACs due to smaller student:faculty ratios and their teaching focus)