Here are some rough-and-tough numbers:
If the customers are so small they are basically paying out of their own pockets … then 80%+- will pay monthly. 20%+- will pay annually to save money. But most work rather skip the discount.
Once the customers get large enough, and you have a brand … in the enterprise, for six figure deals … almost all will want to pay annually via invoice. Anything else is way too much trouble to get through procurement, accounting, etc. And while it’s your budget — it’s not your money.
The more you are between these two ends of the spectrum, your ratio will likely be in-between.