It's a little bit different with (old lady) Europe. Like everywhere, you'll primarily pay trademark but accompanied with quality in ‘this case’! It's well known, for instance, that European Castrol Syntec is synthetic oil while US version is not. There are more oil manufacturers in Europe, competition is harsher and that obviously results with better quality.
I hope that you can find more precise answer about US synthetic oils at http://www.amsoil.com/products/atm_testing/index_flash.aspx
but, because of unavailability in Russia eliminate Amsoil and check what happened with other oil brands. Several oil tests are performed and based on obtained results make your own conclusion about preferred brands.
If I were you I wouldn’t stick with ‘native oil’. It is OK to follow recommended viscosity but forget about ‘recommended manufacturer’. That is only money game! It is more than sure that your car OEM has financial interest in recommended brand. Doesn’t it sound strange for you that only one oil brand, among hundreds of others, is ‘the right one’.