I think Man City are in great goalscoring form and Shakhtar are unlikely to have what it takes to stop them from socring a lot of goals. Still, there is a chance they might actually get a goal themselvies which might motivate Pep's men to push for even more goals. So I expect a high-scoring game.

The other option I voted for is Real vs. Dortmund. Both sides can ship a lot of goals while neither is rock-hard at the back so it's possible that the game would be open and both teams will be able to score a few. I see Real's supposed bad form currently as more of fluke and I think they will be quite motivated to do well against Dortmund who were the only team they were not able to beat in the Champions League last year. And with both teams likely to score some, this game has a very decent chance of offering a lot of goals.