The first one. Thank God. I was so bored with the first four games. The few interesting moves have all come from Magnus, but it's felt like watching two computers play.
I was going to say this exact thing the other night, but got tied up in my other response. So far Fabio has played like he is waiting for Magnus to get frustrated/bored, and play too aggressively looking to exert dominance. It's a fine strategy that could get under the skin of even the best players, but I don't think Magnus is one. He doesn't mind playing closed positions, or playing in inches.
Still, credit for Fabio with that offered b4 gambit in the opening. That was the first somewhat daring move with an intent to initiate I think we've seen from him in the first five games. Watching them counter threats with threats was at least satisfying to watch versus what we've gotten so far where each of them is running around the board putting out the tiniest fires rather than trying to start a big one, and see who can hang on.