Short Answer: You should buy Office 365. Done.
The long answer....
First determine if you need:
- Outlook
- Access Databases
- Publisher
- Use it on more than 1 computer
- Use it on mobile devices
With Office 365, you also get the ability to do "Office on Demand", which means you can log into your Office account, then load "local" versions of Office on a computer temporarily. This could be useful if you are not near one of your computers and you need to use office. Office 365 also gives you the ability to edit (not just view) office files on the ipad (new as of March 2014)
Check out some of my estimated comparisons in this chart. Assuming you will install Office 365 on at least 3 computers, it seems like the best option. Yellow highlights yearly cost of 365 yearly vs the 1 time purchase costs over the course of 4-6 years.
Here is Microsoft's chart and their recommendation -- http://office.microsoft.com/en-us/buy/compare-microsoft-office-products-FX102898564.aspx
Here is a chart and some advice/details.
http://www.entec.co.uk/software/microsoft/Office-2013-and-365-comparison-sheet.pdf
As for Office 365 for Business...that is a different animal, cost is about $10/mo per user for Office with Access, Outlook.
As for Office 365 for Business...that is a different animal, cost is about $10/mo per user for Office with Access, Outlook.