Copied from my response to a similar thread in Commuting just a bit ago:
FWIW, I just bought my son a Giant Defy 5 for his birthday. It's a nice looking bike and it works. He likes it. Shifting is noisy but it works. We also have a few Specialized bikes in the family and a Specialized was my first "nice" bike.
In your price range any of the options you have listed should be a solid choice. If you expand to the $1200-1400 price range you will get much better components which may or may not matter to you at this time.
As others have said, ride any bike you can to get a feel for what works for you.
My personal advice will be to stick with the $700-900 price range for now. Most likely you will be searching for a new bike before too long and you will be more experienced and have a better idea of your likes and needs on the next purchase.
To expand on this advice - I think carbon forks DO make a slight difference in rideability but you will have to ride both types to see if they do for you. Believe me (and I'm sure everyone here will back me up) you'll be looking for ways to improve your ride in no time. You really can't go wrong with any of the 'big name' manufacturers in your list or Giant, Fuji, Jamis...the list goes on. All will be very similar as far as features and components within that price range. Ride as many as you can and pick the one that "feels" best. Fit and feel should be your priorities.
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