With fairgrounds in the kingdom you can probably expect more green cards to be bought than normal, so silk roads do promise more vp. I'd have said that the silk roads are more important than the fairgrounds, so unless you can grab the 15 different cards easily you should look to get a majority of silk roads then pick up 4vp fairgrounds, duchies, and estates, all of them boosting the silk roads. Although there are a lot of different ways to play the two games, I'm guessing this applies to both.
It's worth remembering that you need a lot of fairgrounds with an extra 2vp each to make the 15 cards worthwhile. There's also no point making a deck with the 15 different cards that finds it harder to buy fairgrounds than a conventional deck would find it to buy provinces. That is probably the case in game 2.