Well, I’ve always liked the fact that UMass has the five college system. However, in the case of astronomy, those other, excellent colleges in the five college system, such as Amherst College, do not likely have any facilities or resources in astronomy that significantly enhance the astronomy offerings at UMass. Other things and experiences, yes.
I stand by my assessment that the OP should choose his school, if he plans to do advanced study in astronomy-related fields, with the strongest departments and faculty he can receive in the natural sciences. Thus far, unless he is accepted into Washington, I’d still recommend Stony Brook. I’ve had the opportunity to do some research in the natural sciences at S. B. (not astronomy), and the facilities, research and the faculty I knew personally were quite serious and talented.
I also graduated from an honors program at another flagship university with some outstanding natural science departments. My experience is that an honors program will not necessarily make up for lackluster departments if you plan research or graduate work, but: if you participate in honors and your departments / majors are already strong, honors can enhance your program, and give you more individualized attention, more focused peers, etc. etc. This is not to imply that UMass is necessarily lackluster, but its overall US News ranking has little to do with its astronomy and physics programs, which probably are not as strong.
Finally, with an international poster, I’d be extra careful steering him, as he has not been to this country and may not understand everything we do here. I’ve also lived abroad, so I can sympathize with the situation.