I purchased the Pioneer 4400 this weekend and I like it. Although, all I can compare it to is the stock stereo that came in my 99 integra...but the difference is night and day, so I am very happy I bought it.
I was also looking at the Alpine model you listed, I liked the Alpine controls better, the Pioneers are a bit cumbersome and confusing, but the Pioneer offered more features. I think they are both fine stereos though from what I've read.
Good luck with your choice!