First impressions, the SmallRig does not inspire confidence. First, the shorter, vertical bracket has enough flex to press it against the body of the camera, something that does not happen with the RRS brackets. *See update in my next post below.
Second, the silly holes drilled into that vertical bracket seem too close to the inner part of the frame, so there is only about a ONE MILLIMETER "skin" of aluminum remaining where the holes are closest to the inner surface. Why does smallrig use these holes? Weight saving? Style? They just give the impression of weakening the structure.
Third, big flat-head screws are used to tighten the bracket to the body and to tighten and loosen the sliding portion. There is a dime-sized "screwdriver" magnetically attached to the bottom of the plate; however, it can very easily be bumped out and lost forever. Without that, if the plate needs to be tightened, or the sliding portion adjusted...Who still carries coins in their pockets? Ok, so now we'd need to keep a wide bladed flathead in our bag--or I suppose we could just keep that little round flathead (included with the bracket) in a bag.
Irritatingly, there are small hex-screws that fasten the vertical bracket to the horizontal, but SmallRig does not include a hex-wrench for these. Out of the box, or when first attached to the body, it would be nice to be able to give those little hex-screws a quick check with a wrench, tightening if needed. Purchasers will have to find the right hex-wrench to be sure the two brackets are securely attached.
Finally, it definitely feels chunkier (and clunkier) on the bottom of my R6 than any RRS bracket felt on a FF dslr.
Of all the points above, the unsettling amount of vertical-bracket flex is the deal breaker, in my opinion. *See update in my next post below.
Yes, it is only $30 USD (plus $10 shipping from Shenzhen) , so we get what we pay for. But when it comes to attaching a body and lens to a tripod, I don't want a dubious, cheap piece of hardware. I couldn't resist trying it for the money. Will I be able to ship it back and get a refund? Even if their customer service arranges it, I'd likely have to pay $10 or more for return shipping, meaning my actual refund would be worth about $20. Probably not worth the hassle unless I'm just trying to "make a point."
In the meantime, as of right now, Kirk's L-bracket is in stock, but RRS is not. Kirk doesn't have a sliding plate to pull the vertical bracket away from the ports; nor does it have a hex-wrench tucked in the bottom of the bracket. But otherwise it looks solid, and they state the type of aluminum used (unlike smallrig). A little vague as to whether it is manufactured in the USA, but I'm not sure that is an issue.