If your kid is getting academic scholarship offers to ASU, I would encourage him to go there. Yes, it's a big school and he may have a number of classes with over 200-300 students. But, if he is looking at such a specialized and scientific major, the "bigger" school would more likely have better resources for that.
Also, one other thing that people don't always consider is the network of alumni that a bigger school has. Across the country, the name Arizona State is going to be more well-known than Hastings College. Also, if he is a sports fan, it's going to be a lot more fun rooting for Sun Devil teams for the next 50 years than Hastings College Broncos teams.
I know big colleges aren't for everyone, but I think the bigger school is the better option in the long run.