As a Real Adult living in the Real World (

), I would
not encourage you to use a credit card for all purchases in college. I would encourage you to have a credit card and charge about 10-20% of the maximum every month, then pay off the entire balance when the bill comes, but I would not encourage you to use a credit card for everyday expenses. I can talk more about building credit scores when and if anybody cares.
If the decision is between a debit card and Techcash, I am more ambivalent, but I still think Techcash is a better choice because it allows you to more carefully monitor your food purchases. But I lived on West Campus and I like compartmentalizing my spending -- I still put money on my Harvard ID as a grad student, because I like knowing when I've spent $20 on candy bars and soda.
At any rate, there's no reason to commit yourself to one method or another. You might as well try Techcash and try paying for things with a debit card and see which one works better for you.