The main competitor in the , , has a very straightforward rate: 2.75 percent per swipe for all credit and debit cards, with no additional fees. If your business does less than $250,000 in transactions per year, you can sign up for a flat rate of $275 per month.

mobile payments processing system also offers two options. With no monthly fee, it charges 2.7 percent for swiped transactions (all cards), and 3.5 percent for keyed-in transactions. However, if you opt to pay a fee of $13/month, the rates go down to 1.7 percent and 2.7 percent, respectively.

is ever-so-slightly cheaper than Intuit, with all card swipes costing 2.69 percent, and all keyed-in transactions at 3.49 percent. For keyed-in transactions, however, PayAnywhere also charges $0.19 per transaction.

Other have similar rate plans. As you can see, the best mobile payments processing system to use will depend on how you do your transactions. That said, Groupon's system looks pretty good, so long as the transactions exceed $16 and aren't from American Express cards (Square's swiped transaction charges are better for transactions under $16, because Groupon charges $0.15 per transaction).

Groupon's new payments system will also let merchants get paid faster: overnight, instead of the typical two-to-three-day wait for money. Its supplementary online Payments Center allows merchants to view a transaction history, check sales reports, and track deposits. Plus, a dedicated support team is available by phone and email seven days a week.