So we all can assume you don't even know what Sony head unit we're talking about here ...
But back to the original question ... try and play with both units and decide for yourself. No use in getting something you don't like. Honestly, I'd run both head units in my vehicle. Don't be fooled by Sony's lousy reputation when it comes to mobile electronics ... the cheaper items are lousy, but the 9900 is far from being some cheap piece of crap. Still a pretty decent head unit. The only problem I can find with the 9900/9905/8800/ is that the buttons and face seem just a touch on the flimsy side. Not really something I'd want in a ~$600 receiver.
I'd probably wind up taking the Alpine. But it's just my opinion.
- Steve