Test three: Syncing
Personal productivity systems must be with you even when you're not in front of your Mac, so synchronising tasks - either to a website, other Macs, or an iOS device - is very important.
All of the applications except Onlytasks and TaskSurfer have dedicated iOS companion software, which can synchronise directly over your Wi-Fi network. OmniFocus and TaskPaper can also sync over the internet (via a service called SimpleNote in TaskPaper's case), and this is also being planned for both Things and Firetask in the future.
Onlytasks and TaskSurfer use third-party online services, both of which allow their tasks to be edited through a web browser. Onlytasks uses Evernote, a popular notetaking service, while TaskSurfer uses the excellent ToodleDo online task-management system. Both Evernote and ToodleDo have iOS apps, effectively giving these packages iOS clients too.
Test four: Managing projects
Although none of these apps should be considered full-blown project management packages, the ability to create and organise projects is a core part of the functionality of any task-management software. Projects come in many guises, some of which have to be completed step-by-step (linear projects), while others can be completed in any order.
OmniFocus offers the widest range of project types, including a type that is simply a collection of to-dos that can be completed in any order. This is also the default project type in Things, while Firetask lets you quickly see either only the top action in a project or all of them - giving both project types in one.
Onlytasks and TaskSurfer use different terminology for projects (notebooks and folders). TaskPaper's projects are simple sub-lists in your main document, but its broad tagging system compensates for this by allowing you to customise what you see.
The best productivity tool for OS X is...
These are personal pieces of software, which makes it very hard to name a single winner. Everyone's approach to managing tasks is different enough to make it worth your while trying out at least one or two different packages to see which one suits.
We've whittled it down to a choice of three products: OmniFocus, Firetask and Things. OmniFocus is the 'big beast' of task managers. There's almost nothing you can't do with it, if you're prepared to tinker to make it work for you. Things combines a powerful tagging system with a great look and feel.
But our final winner is Firetask. It's nicely designed, and anyone that's new to task management should get to grips with it in minutes. It's also powerful and has a trusted system.