I thought I'd make this thread to talk about my experience with both products to add to the general knowledge pool.
Simple Green takes about a day to loosen the paint. It gets under the paint and kind of pushes it up in sheets allowing you to brush off large flat parts easily. It works *much* better on metal miniatures than plastic in my experience, and even then, expect plenty of work with a tooth brush and exacto blade. As you may know, Simple Green is generally safe to handle and non-toxic, but performance wise I'm not completely satisfied. Simple Green also has a tendency to weaken super glue bonds over time, which may or may not be a selling point for you.
Purple Power, which I just tried recently works much faster. It does better at actually dissolving some of the paint allowing you to rinse the majority of it off with hot water. About an hour's soak was all I needed. Purple Power is however pretty caustic and will irritate your hands and eyes, so gloves and good ventilation are recommended. You can however wash it down the drain like Simple Green, so elaborate cleanup procedures are not needed.
P.S. There are many brands of 'Purple' all purpose de-greasers and I'd imagine they work about as well as what I used. Check the active ingredients.