Yah so this is the age old problem.

Big companies do really big thing. Google is literally changing the world. But if you get a job there, you are employee #145,231. Maybe if you work hard for 5 years you can rise to the rank of middle manager, and attend a meeting with someone that reports to the CEO, and maybe you can try to get a project you want done scheduled. More likely you will just do the work you are assigned until you quit.

Now a startup is the opposite. Blank startup has no power to change anything. But within that startup, you have 100% voice. If you work really hard, in 5 years maybe your startup will be big and you can change the world. Or more likely, they will go under or get bought out and you have not changed the world.