Since I have 3 different popular cage types I thought I'd spend a few minutes comparing them using the Cynova adapter and my frankenrig microphone which is a pair of AKG C98's in a 3D printed enclosure attached to a Polaroid cold shoe mount.  The polaroid mount works but I don't like the thumb screw arrangment.  I 3D printed my own thumb screws but it still doesn't feel great, I'll revisit it one day but for now it works.

DJI Cage

Not much to say on this, it works if you buy a cold shoe mount adapter.  I got the Ulanzi adapter and it's actually really good and cheap.  So this is the cheapest option for a cold shoe adapter.  The camera has to be removed to access the battery.  Clearance around screen edges is adequate but it is still not easy to grab left, top and bottom screen edges for swiping.









PGYTech

This cage isn't very expensive, it has a cold shoe mount and a 1/4 mount on the side.  The Cynova adapter fits in a similar fashion as per the DJI cage, I have no problem with the fitment.  The camera has to be removed to access the battery.  I actually find this cage a bit annoying to open up.  The casing around the screen edges is deep and close to the screen edges  which would make edge swipes difficult.









Smallrig

This cage is expensive but it is solid being made of aluminium.  I didn't attach the front ring because it obscures the front screen (not that I use that screen much).  If you don't want to use your front screen then attach the front ring to add a lot of protection to the front lens cover - in this case if you're using filters, use 52mm options that suit.  The Cynova adapter fits into an in-set cutout in the cage although I wouldn't really call it any more of a solid fit than the other cages, it is slightly more protected from knocks.  Make sure you buy the *new* Smallrig cage designed for the Cynova adapter, if you buy the original OA cage it will not fit the Cynova.  The cage has a 1/4 mount on the side in a similar fashion to the PGYTech, it also has threaded mounting holes all over if you feel the need to deck out the little OA like a movie camera with lights or handles etc.  One thing that sets this cage apart is you do not need to remove the camera to access the battery, there's no reason to remove it at all.  In that respect this cage is more difficult to open than the other two if you lock down the thumb screws with an allen key.  The cage has the cold shoe mount as part of the cage like the PGYTech.  As for screen access, I'd say the Smallrig beats out the other two for access to the edges for swiping.  It offers more room around all edges and is also bevelled at the inner edges so your finger gets to the edge easier.  The cage is heavier if you're weight conscious.










That's it, I hope this helps your cage purchase decision.  I bought the PGYTech because I knew at the time the Smallrig wouldn't fit the Cynova.  But while the PGYTech was in the mail a forum member mentioned that Smallrig had the new adapter, that's the one that I really wanted so I ended up with both.  I'll give the PGYTech to my niece, she recently bought an OA after looking at mine.

Thanks for sharing.  I keep to the Original one over any other  cage, just me.  I do not like the height of the  top parts on the Original as that can pop open the  clamp, in my eyes.   I already had the clamp pop open with my attachments on there . so I  keep things compact, how I like it.  Again thanks for the share and  it should help see what's out there in here a lot easier for all?

FISH

It does add a bit of volume to the camera
Nice shots.

Got my eye on the Smallrig, shame it's so expensive!

Thanks for adding your thoughts, people need more than new and shiny reviews, they need to really know what sets options apart.  I didn't really think about the original cage clamp popping open with added leverage on top but it is a real possibility.  Smallrig is great if you don't care about weight or volume but it is expensive, all these optional extras add up to one expensive package.  These camera shots were done with my Google Pixel XL V1, it's a great little camera especially if you pay attention to getting all your shots in focus ;).  I rarely if ever use my (comparatively) huge and heavy Nikon D7000 anymore, little cameras like the OA and just the camera on the phone are too convenient.

Hello and good day ebswift. Thank you for reaching out and for sharing these amazing information with us for the DJI Osmo Action. You did an amazing comparison, great work and thank you for your valued support.

I just did a long and detailed comparison of features of the few metal cages that are available for the OA.  Mainly because I hope to mount my camera on outside of an airplane so plastic parts do not meet strength requirements.  I was leaning towards the real nice and well made Smallrig unit until I saw a great review of the Tilta Full Camera Cage.  The Tilta TA-106-D has full accessibility to buttons and battery as well as being compatible with the audio adapter.  So I ordered one here https://www.adorama.com/iatat06d.html  Certainly not a low cost or cheap choice but it should be included in any list of potential cages for the OA.   Here is a review of the cage while in French language you can see by watching the video all of the features of the cage: https://www.youtube.com/watch?v=LD3Iw_MB0U4  Hope this is helpful to someone.   
And here is the one that convinced me: https://www.youtube.com/watch?v=CgGULgAHffg