I wasn't able to watch Med-Novak yesterday, so can't vouch for how well Med played, but the Thiem-Rafa match was very high-quality, so I'll lean that way.
We'll see, first, if Rafa can beat Stefanos and Novak can get by Zverev. My sense (though I'm a bad prognosticator) is that just one of these will happen.
I rarely vote on these, but why are multiple votes allowed with a menu of two items?