There are a number of fervent MLO advocates on this forum. I tried both MLO and AP before going with AP. Since I made that decision, both applications have evolved considerably, so I still test out MLO periodically to ensure that I am comfortable staying with AP.
I participate on the AP forum and make frequent suggestions to make AP work well with GTD.
Tomas has done a great job starting the comparison. I agree with a lot of what he wrote. A few of his comments have prompted me to make the following responses:
Tomas D.;59241 said:
As for views on the data, MLO is more flexible when it comes to filter out the data you wish to appear. It allows to setup many powerful filters.
AP is more flexible when it comes to what for data/columns you wish to see in the view, since AP is column based, but MLO only displays item text and date due in the todo list view.
I have found the filtering capabilities in AP to be quite powerful. What keeps me with AP is that I do have the ability to create views with my own customized columns that I can filter.
Tomas D.;59241 said:
MLO has task dependencies (don't show X until Y was completed) and "complete subtasks in order".
MLO has archive functionality.
AP has always had task dependencies. It has MS Project-like power in these dependencies. You can do many-to-one, one-to-many, finish-to-start, start-to-finish, finish-to-finish, and start-to-start dependencies, and you can specify time lags.
MLO bills itself as more intuitive and quicker to grasp. I think that this is true. You can get up and running in MLO faster than with AP.
In the final analysis, what keeps me with AP is the flexibility of the column-based views. For any action or project there are a handful of fields that I always want to see. For me those fields include: start date, due date, person assigned to it, and context. With AP I can create a view that shows me exactly what I need to see all in one screen. If I want more detailed information, I can double-click on the item and deal with it in greater complexity. With MLO, I have to click around to find what's important for me to know.
AP has the flexibility to show me just what I want, just the way I want it. The tradeoff is that AP has greater complexity and takes longer to learn.