There are three popular desktop accounting systems. We're not including cashbooks or less popular systems. You have three main Kiwi options - MoneyWorks, MYOB and Reckon.
Moneyworks has a cash-book, two main levels of product (Express and Gold) - and a more major multi-user version. Designed for the Mac, the PC version is basically the same from an accounting perspective.
MYOB has a cash-book, but the AccountRight series also comes in various levels - Basic, Standard, Plus, Premier and Enterprise. As well the AccountEdge series has three main levels - Basic, Pro and Network.
A difference between MYOB and Moneyworks is that Moneyworks has the same product for Mac's and the rest of us. MYOB has AccountEdge for Macs and AccountRight for PCs.
Then there is Reckon (formerly QuickBooks). Like the others, it has several versions - Accounting, Plus, Premier and Enterprise. Note these are now only available on a subscription basis - you can no longer update them every three years or so.
First, eliminate those which don't run on your platform. Then choose between the competing products without worrying about the levels. Basic functionality is much the same - after all accounting is fairly basic. But there are differences in the look and feel - how you use the product. The only way to be really informed about this is to get your hands dirty - to see what happens when entering an invoice or a bill, and when paying or receiving payment. Reconciling bank statements and doing a GST return is also something worth trying. Also, of course, you may need special features - e.g. contract retentions. There are too many possibilities to cover here - but they should be top of your personal list. Another issue is how will you work with an accountant on this. There are different ways each handles this.
Having chosen a product, you can then narrow down the series that you want. Basically the more you pay the more features you get. Some include payroll, and some don't. If you use payroll then that is something you will have compared above, and basically means you have eliminated Moneyworks since they don't offer it. Of course, you could still run MoneyWorks with a separate payroll. In fact, it's almost essential to run payroll on-line regardless of the desktop.
A word on levels - you can always go up another level (unless you're already at the top) but you can't go back down. While it sounds like a marketing trick, there's also the problem of extra features having extra fields. There's no easy way to accommodate the loss of these fields.