The best way to go about picking up the pricing plan is by assessing at what stage your business is at. Are you just starting up or are you an established business? If you are a startup go with the startup plan and if you are an established business then go with the enterprise plan.
This choice entirely depends on your commitment to the online business and available funds. If you are willing to invest for a year then you may go for the yearly plan and avail of 2 months of free period included. If you do want to have a high upfront cost then you can choose to go with the monthly plan.