Back to the OP question on what is the best OIII
For most of the nebulae dominated by the ionized oxygen, including the popular deep skies candies, the 12nm passband OIII filters, like the Lumicon and Astronomik are certainly the best and the most popular choices, and offering the best observing comfort. No way around.
On the difficult-to-see OIII nebulae, the 12nm passband may turn out to be too wide and passing too much light not used for seeing the nebula - either plainly distracting, or lowering the contrast.
This is the reason, why Baader has designed the narrower OIII filters, and why Astrodon has later designed the extra narrow passband filters, the 5nm and 3nm.
So, it is not the question which is better and which not, but for which specific nebula you will take a filter with a matched passband, similarly to the astrophotography. It is just the spectral filtering of light on purpose.
The good message is: These all filters can be purchased for money.
The bad message is: The costs increase as the passband width decreases.
The comment to the bad message reads: You won't always need a very narrow passband filter.