Graduating in 3 years a good idea?

I am a junior at a top 3 engineering school majoring in computer science. I have the option of graduating in 3 years vs. 4. If I graduate early, I will likely work at a startup or do a startup of my own. The main benefit I see of staying the 4th year is it will allow me to take a few more cs classes which will help with grad school admissions. If things don't work out with startups I would like to be able to do a masters in cs at a top 3 school. I have a decent gpa, i'm in the honors society for my major, have some research experience, and several internships under my belt.