I own both a Galaxy S (Vibrant) and a 1st gen WP7 (Venue Pro).
There are certain things the Vibrant's extra horsepower allows it to excel at - for example, Fruit Ninja (the only game I have on both) runs quite a bit smoother on with the Hummingbird's much beefier GPU. I can't really compare media performance because I don't watch videos on my phone.
However, when it comes to navigating the OS, transition animiations, scrolling/zooming in the browser, even page loads in the browser - the Venue Pro isn't just better, its not even a comparison. If you didn't know better, you'd swear the VP was several generations ahead in hardware, not behind.
Having powerful hardware is a good thing - but the fact is, its not everything. Well written, optimized software can quite often make a much larger difference. And I don't just say that because I'm a software engineer