I bet you haven't researched medicine yet. Or else somebody beat you to it.
-g
Only if SP was not worth it in the first place (empire too small)If you have sufficient resources, and place the HQ in a city with good +Weath modifiers (Wall Street city preferably) the benefits can outweigh what you get from SP once you spread the Corp around. Even more so if you grab a 2nd corp.
Of course, you have to invest quite a few hammers to spread it around.
Only if SP was not worth it in the first place (empire too small)
Why would one go SP with a smallish empire
If you dont need SP for maintenance, then Corporations (and other economic Civics) outweight the 10% hammers from SP.
And while Corporations do indeed get better with access to more ressources and with more cities to benefit from them. But they can not offset the massive distance (or possible even colonial) maintenance of a big empire.
Best way to start with Sushi Corp is to put the HQ in your best commerce / financial city, then start spamming executives to *other* civ's cities. Make them pay for the maintenance, eh? You get the profits.
I typically only spread Sid's Sushi to a handful of cities in my empires, mostly cities that need extra food.