Take a moment to consider what your needs will be besides carrying your laptop and which style will work best for you.
Messenger bags are ideal because they are so versatile with the options in compartments along with the ease of carrying by hand or a shoulder strap.
Rolling Laptop bags are very nice for people who travel a lot with their jobs or for people who have to walk long distances with their computers in tow.
Backpack style bags work well for the hands free carrying options but also do not give the appearance that you are carrying a laptop inside. That might be a wise option if you fear that someone might be in the area that would take a bag if they thought a laptop was in it.