It depends on what you want really. I'm also deciding whether to go with Prorata or not.
Its kind of an advantage for a business as they get all their money near enoigh on the same day so it is easier to manage and keep track of throughout the months where you haven't got money flying in and out from everywhere.
However from a clients view they may not like paying a little bit extra because they pay half way through the month. I'm currently with a host that uses prorata billing and it didn't reall bother me paying a few extra bucks because i paid a few days before the end of the month.
From a personal point of view, could you imagine the influx billing related enquiries on your chosen billing date if you go for a pro-rata system? It seems better to spread that support load through the month.
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