I'll offer a slightly different viewpoint. IMHO, there is a significant different in ride quality and speed between a touring bike and road bike (eg, racing or sport touring). I have two touring bikes (Bob Jackson World Tour, Soma Saga), a sport tourer (Waterford RST-22), a racing bike (De Bernardi) and a cyclocross bike (Ritchey).

I would not get a touring bike unless you are planning to do loaded touring, commute with moderate to heavy loads, and/or need wider tires for gravel or unpaved roads and trails. Touring bikes are made with stronger tubing and thus have a stiffer ride than most road bikes. To ride comfortably, you almost need to use wider and thus heavier tires. They usually have a longer wheelbase, so they feel relatively sluggish and slow. They also tend to be heavier. That said, I love my touring bikes for their intended purposes -- loaded touring, commuting and riding on unpaved surfaces.

In contrast, my racing and sport touring bikes feel like sports cars. They are lighter weight, quicker to accelerate, handle better, and ride smoother on rough pavement with narrow tires. My Waterford sport tourer is a great compromise because it has mounts for fenders and racks, clearance for larger tires if needed, and reasonably light. I have ridden it on many long rides and supported tours, and wouldn't hesitate to ride it with a rear rack and panniers with no more than about 20 lbs of gear. I often commute on it with a large Carradice seat bag. However, if I am planning to carry panniers and heavier loads, the Soma is my bike of choice because it has no flex whatsoever and can handle larger tires.

I have commuted on all of my bikes, and it takes me about 5 minutes longer each way (15 miles) on the touring bikes, so they average about 1 mph slower. The Waterford is my favorite to ride, but I am somewhat anxious of getting it stolen. I end up riding the Bob Jackson touring bike most often because I've got it set up best for that purpose, and it's a little lighter and quicker than the Soma. My Ritchey cross bike is a blast to ride on unpaved roads but I don't commute on it very often because it doesn't have fenders, and I don't want to put them on it.