Personally, I'd go with a touring bike. Steel frame, 36 spoke wheels, and 28mm tires. When I was new to biking I thought I would need to get be a "fast" bike. I started with an aluminum frame Specialized Allez Elite w/carbon fork. I didn't particularly think the ride was that rough on the roads I was riding and bike paths. I had 23 mm tires as 100 psi. I wanted to be on my bike anytime that was feasible... this included commuting, family rides hauling gear, as well as fitness/conditioning rides. Well, the road bike wasn't built for all these things. I also have plans to do the Seattle-to-Portland bike ride in one day. I found that 3 hours on the road bike was about the max I could stand without at least an hour or two rest.. then I got sore sooner than 3 hours on the next leg.
So, even though I got a great deal on the road bike from craigslist, after 6 months I found myself in the market for an "all-purpose" bike. I road a steel touring bike (trek 520) and I fell in love with the feel of this bike. The touring bike met all my needs... great for commuting (racks, panniers, bags), It's very comfortable.. I could stay on all day, It's fast enough for me at this point in time.
I rode several touring bikes. The best that I could afford that had all the features that I wanted (STI shifters - bar ends are usually what are on touring bikes) was a bike called the Rocky Mountain Sherpa 30. You can see pics and posts in the touring forum. Anyway, I can see myself keeping this bike for a long time and riding it daily as my commuter, and doing all my longer rides on it... 50-200 miles.
I still love the way race/road bikes look. And they are fast! Maybe someday my level of fitness (and weight) will be ideal for riding a road bike and doing long rides. But the road bikes are too stiff for me to stay on a long time. And if i'm going to keep cycling and getting in shape, my bike better be a joy to be on for long periods of time.
Now granted, I've heard good things about carbon fiber. I don't know how well they hold up to the stress of clydesdale weight and as a beginner, my bikes get banged around a bit.. I'd hate to bust up a 1500-3000 dollar frame. (plus.. you aren't going to carbon fiber for $700)
So, at least consider a touring bike. At least test ride one. It may serve more purposes than you intend as you begin your cycling life. And, if you decide against it, at least you can say that you did your homework.