Here's a quick summary of each one:
- Protube - ultra lightweight, good mounting mechanism and very sturdy. A solid choice. Cons are that the foregrip is also magnetic, and bottom mount means awkward reload. Stock is not too comfy. Excellent adjustability makes it useable in all games. Magnetic snap is slightly too aggressive and can cause tracking to go haywire for a short period.
- WieldVR Onestock - Flimsy piece of plastic. Never even made it into a match, straight in the bin.
- RavenVR - Overdesigned with too many features that aren't actually useful. Entire thing is very rickity, with a lot of wobble on the rear magnetic grip especially. Also too big and heavy, which also makes the tracking unusably bad because it makes it very difficult for the lighthouses to see the controllers. Foregrip feels good when locked in place at the closest setting, but the magazine grips feel horrible and have zero tracking.
Has a cool pistol grip on the mounting mechanism, but also feels very claustrophobic as you cant stretch your fingers. Zero adjustability.
Ultimately I think if the creator of this used what he's learnt to create a lightweight/slimmer version with the wobble/finger restriction gone, it would be the best stock. As it stands, weight, tracking and shakiness make it very awkward to use.
- Olen VR Spine - Very solidly built, but the mounting mechanism is trash. Magnets detach from the slightest pressure in any direction, always dropping it by accident. Generally feels a bit awkward to use as it's quite heavy, and the weight is weirdly distributed. Magnets are right above the thumbstick so you can't move your thumb properly. Zero adjustability.
- Olen VR Asset (SBS) Mod - This is the one that's like a tube you can snap in the middle. Ultimately ends up being the worst of both worlds as it's awkward to snap back together instead of just using a non-magnetic grip for the front hand. Feels really awkward and heavy when not connected, and also makes it impossible to use pistols comfortably. Zero adjustability.
- Virtual Rifle Systems MK3 - The absolute GOAT. Rock solid, non-intrusive mounting system. Used two magnets on the one controller meant you could only detach it by rocking your hand backwards and releasing the rear magnet first, but you can still pull the stock hard into your shoulder otherwise with no chance of accidental detachment.
Foregrip is just a normal rifle grip, but hollow so your fingers can activate the grip sensor. Lightweight, top mounted, somewhat adjustable. Very slim profile with a hollow dust cover to allow better tracking. The company that made this is now out of business, so I am stuck searching for a useable alternative if anything goes wrong. (also tried their SBS stock just before they shut down and it was complete crap). Picture of mounting solution so that anyone in the stock manufacturing game can steal the design (please):
Anyway, hopefully this info is useful to someone. I wish index had as many options to try as quest.