I would take Aventus. It isn't my favorite scent, nor is it the one that gets me the most compliments, but it is excellent, and it's easily the most versatile scent I own. For a 6 month trip, I would value versatility above all.
I think this thread is fun to think about. When I was a kid, I applied to be a foreign exchange student. The first month after being accepted into the program was bizarre because I had to wait about six weeks before I'd find out where I'd be going, which made it impossible to know how to prepare. I ended up spending a year in South America, and I loved it. One of the most important lessons I learned was that preparing for the unexpected is always a wise way to go.
In the end, versatility is key. So... Aventus isn't my favorite, but it's perfect for preparing for the unknown. It's formal enough, yet casual enough, flirty enough yet businesslike. It's pretty much a can't go wrong scent. It's nearly goof-proof.