I currently own an Audi A1 S-Tronic, and whilst the gear change is very smooth and all that dreamy eyed stuff, the DSG system from VAG has not been without its problems. There are plenty of posts around on the Internet to that effect.
My 2p worth of advice is to understand that VAG are a very large group of companies and have been working on this sort of technology for quite a few years, plus they have a vast array of cars to drop these gearboxes into and trial.
Volvo, on the other hand, have not had that luxury, but they have been working hard and I personally have only tested 1 Powershift based V40 D2, but it seemed quite OK for what it was - almost the same as my A1 S-Tronic I felt, when driving sanely.
There is a new 8-speed gearbox coming out with the D4 and T5 V40s as we speak, and I am sure that slowly, over the next 2-3 years, Volvo will start introducing that gearbox as an option on more cars.
I have not tested the older technology Geartronic, so can't comment on that, but what I can suggest is if you have not tried a car with one, pop into your $tealers and ask for a test drive in a suitable car.