Nothing,
We all at some point get to a stage where we are comfortable with our equipment, technique, rounds, and when something new comes along its not accepted because we ourselves believe we have the perfect setup and solution already.
I junked my ad's a long time ago, although good, the Constant Spring breakages, excessive wear to the no.1 clamp on gardiners poles and non compatibility with Carbon goosenecks were becoming a pain, the aquatap solved the breakages problem and wear, however long term they have their own issues, causing wear just behind the clamp, a bit like the ordinal gardiners clamps, the univalve, as far as I can see has all the great assets of ad's but none of the drawbacks, lighter, easier to use, compatible with everything.
Darran