Is the Alpina a chronograph?
It is a quartz though, right?
It's a nice looking piece, unusual because you don't see them that much.
Alpina does make good watches and is a sister brand to Frederique Constant. It comes in several different bezel colors, too.
The Oris is a big piece, the grey dial and green bezel look pretty good in photographs. I'd like to see one in person.
If you can pull off the size, I'd go with the Oris, only because I, personally, am not too keen on paying a lot for quartz watches. But that's just me. It may not be a big deal for you.
The Alpina is a nice size and that sucker does look pretty good, though. Plus, like I said, you don't see many of them either, while everyone seems to have an Oris diver. As an Alpina, if it were an automatic, it would probably be $1000 more.
Neither one of these is a dog, that's for sure. The deciding factor will be size and auto v. quartz. At least that's how I would feel.