Master's in computer science or computer engineering -for startups

I am currently working as a software developer and I graduated in Electrical and Computer Engineering 2 years ago. I love both software and hardware fields and I am just not sure which field to choose for my graduate studies. Also, I just don't want the 4 years I studied Electrical Engineering go for waste. Anyhow, my ultimate goal is to start my own startup. Given all these information, which field would best suite for me? which field has more potential for me to be succeed in?