I am just the opposite of you-I think the JDQA is perfect for small and medium framed tractors. It's cheaper, and lighter than the SSQA and just as fast/easy to use.
In my way of thinking, there are only three basic things most people use on the loaders- Buckets, Forks, and Grapples. All three of those are readily available in the JDQA style from JD or the aftermarket. Those three things in the SSQA style are usually to heavy for a CUT to use effectively.
I am not trying to start an argument-just offering another point of view.
Generally, a discussion is not an "argument" until one or more parties become "abusive and/or unwilling to respect someone else's point of view".
So, with the intention of discussing the pros and cons of the SS mount vs the JDQA:
I agree with your assertion regarding the "three basic attachments that most people use on their FEL". That pretty well covers it..
However, there are a number of current Bobcat skid-steer loaders that do not have the lifting capacity of the 300CX loader: S70, S100,S130. Bobcat also makes a couple of track loaders with less lifting capacity than the 300CX FEL.
Buckets, forks, grapples etc. for those models would all perform very well with the 3000 series machine.
The broom, and augers might not be suitable given the lower hyd output - but the 300CX (or even the 300X) would not have a problem lifting the attachment.
Regarding your view that the SS system is "heavy" - how heavy do you imagine that it is? Or more importantly how much heavier is it than the JDQA? 75lbs, 100lbs?
For the sake of discussion: I would venture that each SS attachment end at the curl cylinder is less than 50lbs - face plate and locking lever - but, for discussion purposes; let's say they each weigh 50lbs. Heck, let's say they weigh 75lbs each!!
And the JDQA - how about 10lbs for the hardware; 20lbs total.
So, we have a difference of 130lbs.

That drops the lifting capacity of the 300CX right down to something in the neighborhood of 1,400lbs...
That is not likely a "make or break" weight problem for most users - IMO.
Finally, the availability of SS buckets, forks, grapples and other attachments that can be had for generally, much less than the "hard to find - or impossible to find" John Deere equivalent makes the SS option a very easy decision to make - IMO.
AKfish