In small business it is all about 2 factors, the first is the cost. Mastercard and Visa can be processed for as little as 1.2% whereas square, Paypal and most of the online providers charge as much as 5%. The second is the speed the money flows to the company's bank account. Visa and Mastercard transfer daily, Paypal is fairly quick but you need to initiate the transfer. As for Square and other online I have never used them due to higher fees.