It is common to go into a long macro game on Cloud Kingdom for TvZ. The locations of the 3rd and 4th base are straight forward, but the choice for 5th is quite tricky.
Before I go into the choice for 5th base, there are two things that I want to highlight. Firstly, Terran like to mech against Zerg now. That seems like the answer against Zerg’s early 3rd opening, which basically the most commonly used strategy now. MVP and Supernova were going mech in almost every game in IEM a month ago, and MVP always chooses the best build. If you are still not convinced that it’s the best build now, just look at MarineKing. He used mech against Zerg for almost every map now, despite the result is mediocre. Mind you, he is the marine king after all. That gives credibility to this build.
It’s a cliche to say that the weakness of mech is mobility. MVP showed a tiny trick on Cloud Kingdom in IEM which helps to minimise this weakness. And that is to build a planetary fortress on top of the ramp at the entrance of the natural. This prevents counter attack run by from the Zerg. Lucifron did the same thing in WCS Europe too.
With that planetary fortress, Terran can focus to defend at the 3rd while harassing with banshee and hellion. As the game progress, both players will take more bases. Up till the 4th base, everything is straight forward. Terran can then choose to either build the 5th on location A or B (see image below).
In WCS Europe, Lucifron chose to build his 5th on A against Stephano. For large part of the remaining game, numerous battles revolved around the 5th base at location A.
I will argue that B is a better location for 5th. This goes back to the fundamental tactical positioning that one should attack along the path where their mining bases are. That is, if you have your 5th on A, then you should attack from the left of the map. That is because the attack can provide direct cover for your 5th.
However, while Lucifron tried to defend his 5th on A, his 4th is left vulnerable. It will be better to build the 5th on B, and attack on the right side. This can provide cover for both 4th and 5th base. The planetary fortress which is mentioned earlier on will help to prevent Zerg from counter attacking from the left side of the map. One can even build a sensor tower for more cover. By keeping the battle on the left, the player at the top half of the map is protecting his two mining bases, but the player at the bottom half is protecting just one. Overall, it seems better to have the 5th on location B.