In my opinion, the twin would be better. The Caravan is much bigger and more comfortable, but the Baron will teach you more about flying. Airlines don't give a **** about single time. You will enjoy the Baron better as well. I've got time in both. Over 400 in the Van, and I can tell you it gets boring very quickly. The Baron feels much more intimate, and I think make you a better pilot.
There is also the comfort factor of knowing that you've got 2 donkeys working for you. I don't subscribe to the train of thought that says the 2nd engine only takes you to the scene of the crash. You might not always maintain altitude, but it buys you time.
Good luck.
JF