score:2
You did not say which European passport you have, but assuming that it is an EEA member, then it would be the easiest to use. Overall there is not much difference between the two but the staff are likely to be more familiar with accessing the EEA system.
For your other question, you should answer 'yes' to the question if you were ever in Russia. If they find out that you have circumvented immigration controls by switching nationalities, they will be very upset. I can attest that the food in Sheremetyevo detention defines a new level of horrendous. So it's best to play it by the book.