Freeing Ross is logistically a lot easier and must be the priority. Snowden lives in relative freedom. Snowden is a different story. First, Putin will not let pass the opportunity to mess with the US public opinion, especially knowing that the media is completely controlled by the Dems and the nevertrumper neocons in the GOP, and Russia will continue to be an obsession that they'll gladly exploit against Trump. And second, if Snowden is pardoned and he gets back to the US, his ties with Russia cannot simply be forgotten as a matter of pure protocol. There will be hundreds of hours of interrogation and scrutiny by all types of US agencies, subpoenas, congressional summons, etc. That's a huge amount of heat for Trump.