Bucknell does seem to have more of a party/Greek Life reputation than Lafayette. By the numbers, it appears to be pretty much the same. I think in the case of Bucknell, its rep might be due to its isolation. There is a lot more “life” to be found around Lafayette, in terms of other towns and cities in the vicinity.
Both have an A+ on Niche, but Bucknell has a lot more students. You will find non-partying people at both schools. I would not let partying concerns drive your choice. Partying happens at every school in the country, even schools that have no Greek Life. Go to the school you can see yourself being happiest at.