Having had numerous Gransports with the supposedly 35% quicker gear change and now a 2005 QP5 Duoselect, I would say there is very little difference in the way either shifts, whether in normal or sport. I have never driven a pre-facelift Sport GT, but I can say the earlier Duoselect drives very well as long as you remember that it is effectively a manual gearbox. It changes faster than you could do with a manual clutch, but you will still feel the clutch open and close as it shifts gear, so not like a torque converter auto. Once you accept that you are driving a “clutch-pedalless” manual and adjust your driving style accordingly, eg allow the revs to drop a little as the clutch opens, the duoselect does a very decent job of blurring the changes. This quite quickly becomes instinctive, and the box and car then rewards you with an involvingness that no other 4 seater saloon can replicate. So you should think of your choice between a ZF and Duoselect as between an automatic and a manual, not as comparing two different automatic gearboxes.
Concerning wear, there are two problems here. The first is that there appears to have been some defective clutches that failed early, and this has unfairly created negativity about the cost of maintaining the Duoselect/cambiocorsa gearboxes. The second is that, again, you have to think about it as a manual and learn to drive it so that you minimise the time of clutch take-up to minimise wear, as you would with a manual clutch. There is plenty of evidence that a property driven Duoselect clutch will last more than 50k miles. So buy one with plenty of wear left, learn to drive it like a clutch pedalless manual, and you will have a wonderfully involving manual 4 door “Ferrari engined” saloon in your garage.