no, not personal preference, just experience.
Not that there is really anything wrong with a single piece if it is made right, but when made for street applications, anything over 6000rpm and a 3inch tube shaft 2.5-3mm thick and 1.5m long goes critical. This means that if you put enough torque through it, you'll tie it in a knot. You won't do that even to the factory 2 piece one with the same torque and revs.
2 piece tailshafts are stronger and the load is displaced better over two shorter pieces of tube