Hello. I have 2 sites - first for stories and blog and second for shop, runs on ubercart. Two sites runs on different domain names

Which solutions is best for performance, seo, stability: 1) install all needed modules (ubercart, google analytics and other) in only one site (shop available for example on /shop/ 2) install all modules in separate sites (like now)...?

P.S. Sorry for my poor english.