Russia seeks to derail Ukraine’s trade deal with E.U., deploying taunts and insults

As the Ukraine looks to derail a pending trade agreement with European Union, Putin, Russia's president wants the Ukraine to join the customs union of Russia. Russia, a major importer of chocolate from Ukraine's premier confectionery refuses buy product from them due to a claim of Sanitary Shortcoming in the candy boxes.
Therefore, Ukraine is faced with the options to either choose a path that would open them up to European values of transparency and the rule of law far to the east, or it can join Russia, as stated in the article, in a financial and cultural zone that is increasingly defining itself as separate from the West and not answerable to Western norms.
Ukraine imports most of its natural gas from Russia and would endure major losses if sided with the European Union. It is evident that Russia does not want that to happen. 

Russia, a way bigger world power that Ukraine, has more that it can effect when it comes trade and to set world prices. 

In you were a Ukrainian leader, what would you do or suggest in such situation? Would you side with the E.U or join the customs union of Russia? Keep in mind that the European Union, aside from its financial status right now, just accepted Croatia in its midst, and is taking on Croatia's bad debts.