I use both LB and OF and like both very much
Life Balance was a GTD-type program even before GTD was first publicized (i.e. the publication of the book in 2001), in that it connects tasks and projects in an outliner with a task list by place (= next action by context). Its original focus was the handheld market, and when the Palm OS was dominant it was (and is) the best such program for synchronizing the data on the handheld version with the data on the desktop, and in particular it has long been supportive of the Mac OS, unlike many other Palm developers. I still love and use my Palm device daily, and having Life Balance synch so well is a major reason why. Still, for the Mac OS alone, Omnifocus has many more features and is much better at sorting and zooming in on projects and tasks, as well as identifying ones "on Hold", "Stalled," (= active but no designated next action) etc.
What Life Balance does that OF does not is to sort tasks (within a context) by a combination of urgency and importance, which is easy to adjust and which makes it easy to see what the most important tasks are that need to be done, not by comparing tasks to other tasks directly, but because the projects that they belong to are designated as most important. In other words, Life Balance makes it easy to quickly choose what the best thing for you to do is; and that is at the heart of the GTD "Do" stage. OF is also good, but it requires more sorting and scanning to get to the same decision.
Life Balance is also known for a feature that I don't use much, but for which it is named -- you can track which areas of your life are getting too much or too little activity and then use the software to nudge you to a more balanced life. This is a unique feature (among several) that MLO copied (possibly illegally) and which is absent elsewhere in the GTD software world.
They cost about the same, I think,so try both and see which suits you better. For me, I like to use LB for all my projects and next actions (because I'm not in front of my Mac all day long), but to do major planning and organizing of large projects, I prefer to use OmniFocus.
George