I honestly don't think you should have any problems in Russia. They have a WC right now - if they wouldn't let anyone in or out of their country, they would have a huge problem ;)
But in the end, you have to decide where you feel safe or not.
I'd say it depends on flight times and prices ;)
But you made me check for flights too and there are direct flights from Frankfurt :joy Sometimes I love living close to a huge international airport ^^