Like other said - fit. All else is far secondary. Next - how fast are you? Until you are riding in the 20 mph range, aero means very little. Over 25 mph it is real. At 30 mph it is huge. Weight counts only on hills and only as a percentage of your entire weight. I weigh 155 pounds. That's 175 pounds even with a super light bike. (Remember - clothes. helmet, shoes, water bottles, tool bag.) 5 pounds saved while riding up a 25% grade will be a 3% advantage. (Since we are talking of a near 15 pound bike, that 5 pounds can only be had at probably a cost of $1/gram = $2300.)
Now, if you race, very light wheels make a very real difference as they take the sting out of the dozens of accelerations you have to make to stay with the group and maintain position. But don't sweat this now. Get the bike, then get some tubular race wheels for race days only.
Again - fit rules. Always.
Ben