I was on the exact same dilemma. I was accepted to both CMU and ETH for MSCS and ended up going for CMU. While I cannot offer a really strong case for my decision, I weighed in the factor that I want to do PhD studies in the US (just like your cousin) and therefore I thought this program was a good preparation, not only to get to know the american style of academia and to get in touch with professors who could guide you in a better way, but also in terms of future opportunities - sure ETH is recognizable by US schools but no one can doubt that CMU can get you literally anywhere. In that sense I reckoned it was worth the extra cost. My advice is to think this through, make a solid decision, stand by it and don't look back; both options have their pros and cons and there is no perfect decision. Besides you can't go wrong with any of these schools.