Which is the best mobile credit card reader?

I have a small business and I want to know which credit card reader I should get for my iPhone.

If your business has an existing merchant account, I would check with them first. If you do not have a merchant account both PayPal and Square offer free credit card readers with competitive rates.

I have both a Paypal and a square card reader for my business and I personally like the square card reader better then the Paypal one. I would highly recommend getting the square card reader.