If we are talking about typical V8s or the Viper V10, I'd bet on the 475hp car.
You didn't mention the rpm and that's important but if both cars get their hp peak at about 5k rpm and they are both typical street engines, the higher hp is going to win.
For a good text on this, look at,
http://vettenet.org/torquehp.html
They have a comparison of these Chevy sb engines
LT1 300hp @5000 rpm 340 ft/lb at 3600 rpm
L98 250hp @5000 rpm 340 ft/lb at 3200 rpm
They also have a very good run down as to what horsepower, torque and rpm really mean to you.
You can't just say hp wins races or torque wins races. You need to know what the curve look's like.