Well, in essence, I guess they are the same since they are both screen printing companies where you can use your imagination to create and design products like t-shirts and then try to sell them. It is quite easy to set up your very own campaign within their websites. You can then select different products; t-shirts, hoodies, mugs, posters and more, design them, and try your luck selling! What is good about both of the companies is that you only really focus on designing and selling; they do the rest like shipping and more. You collect the profit. Easy peasy!
Which one is better? You will honestly hear and read many mixed opinions but I truly believe that if you are a beginner the Teechip is the better option. They have better profit margins than Teespring. I feel like the Teechip's e-commerce tools far better and with more features.