Here is another analysis from science. A 1 trillion joules explosion is a 1 trillion joules explosion no matter what source it came from and it takes exactly one trillion joules to accomplish. It's all about the law of conservation of energy. What you put in, is what you get out.
If it took 1 trillion joules for Hashirama to use Shin Sushenshenju to take down Madara/Susanno, then if he could, he'd be way better off putting that 1 trillion joules into Shinra Tensei since that attack reaches the enemy instantaneously and we get the same exact output of devastation for the same effort.
Another example, If Goku from DBZ wanted to blow up a planet and assume for the sake of argument that he has both the Kamameha wave and ST and he is going to choose only one of them to accomplish this task. Further assume that no matter what, he wants to put exactly 50% of all his energy into whichever attack he chooses. What should he choose? Well, ST of course since it will reach the planet first. That ST will still have 50% of his energy just the same as a Kamehameha, however the ST is simply faster so he should go with that.
Of course, neither Goku nor Hashirama has ST, but these are thought experiments and they show that, if they did, they be better off going with ST.
QED.