I have heard of quick attach compatibility issues on some attachments. Some of these issues are Kubota's fault and some of them are the attachment manufacturer's.
Kubota's issue: The QA mount sticks too far below the attachment. Bonehead Kubota. It should have been designed right from the beginning with the Bobcat skid steer plate as the benchmark.
Look at page 17 of Kubota's Grand L brochure, the QA sticks down too far below the bale spear. This MAY cause a couple of problems:
a) Inability to hook into the top wedge of the attachment when it sits on the ground.
b) Possible scuffing of the loader frame on the ground when using something like a snow plow or a non-Kubota bucket. Not a big deal unless your loader frame made ruts in your freshly paved driveway! Then you're on the phone with the dealer really fast. No remedy for Kubota's issue, just live with it.
Attachment manufacturer's issue: The attachment's QA plate does not conform to the SAE standard. Shame on them. Usually corrected by a little grinder work or a date with the "hot wrench".
Buy the Kubota QA option. It is so simple to switch attachments, you'll forget about compatibility issues.