Alpine definitely.
First thing people notice when they get in the car, and everyone mentions how good it looks. It's also extremely fast and the sound quality is also very good.
As said, there is the Alpine X100 out now, as far as features go im not too sure how different they are.
Some say the X100 looks a lot better, I guess it looks more "high-tec", but it has more fiddly controls, which doesn't help when driving.
WHOOOOPS just ended up comparing the two Alpines
I'd go with Alpine over Pioneer anyday though.