Please, help to choose. 

Freestyle.
Durability is most important thing for me.
Going to use O3.
Weight is not so important.
No GoPro.
Good noise profile is big advantage.

GEPRC Mk5 O3......................    





The SS seems lightweight and overly complex, and looks like a weak point just ahead of front arms?

Beaver more of a tank, much more rigid.

Only you know your ability to give a frame a hard time!

Actually arms on Siren look more rigit:


then on Beaver

I just transferred my AOSo3 build into a Siren F5 Split but have not flown it yet. But like Bad Raven said you're going to have to fly it yourself to see. Most of my flying is around grass/trees/bushes so my crashes would be a lot less severe than someone flying around harder objects. Plus crashes can be so wildly different depending on how they impact. Some of the worse damage I've inflicted has come from what I would would have thought were light crashes. Meanwhile some crashes that you're expecting the worst and you didn't even bend a prop.

While I get it that durability is important to you it's an attribute that is going to be hard to quantify. Yet it's exactly the reason I've dumped the AOS5v2 frame as I don't think it will hold up as well as my AOS5v1 has.

I don’t think the O3 camera will fit in the Beaver 5”?
   I have been looking at 5” frames and the Beaver was at the top of my list but the frame shows up in camera view and the up tilt is limited.



  I have to mention the Footy frame by five33 especially if you fly off of grass when there’s any chance of dew.
 The footy has been designed for a 03 camera and air unit.
 The frame raises the electronics about 2” above the ground and the props are even higher.
 Great for flying off of grass or rough ground.
    I recommend getting the 6” arm version especially if you like using 6S 1400 for the prop to lipo clearance gets tight.
 I have a footy and it’s what I fly during wet weather but I use HDZero freestyle vtx and not the 03.
  
  
  
   

If you haven’t found a frame yet impulserc has a new Apex EVO with a different camera mount for the 03 camera.
 They have switched all their frames to the EVO version.
 Apex is very durable and easy to tune.
 It’s available on website to see.
  
  I don’t know if HDZero freestyle will fit however.
 Walksnail v2 vtx should fit.

Noticed the thread bumped, I've flown the Quadmula split a few sessions and am really happy with it. Since I've added other 5" quads on top of the first quad the Nazgulv2 most of them have been deadcat or other variations of props out of view. A while back flying on a very wet day I reached for the Nazgul and noticed I was enjoying it a little more than my "better" quads I've built. Maybe the X frame suits my flying style over the others. Migrating the o3 from an AOS to this means props in view but I don't care as much about footage. I've noticed the black and clear aren't as noticeable in footage but that also means the quad isn't noticeable when you've got to go find it during a crash.

Props in view: