In addition to looking for good vibration absorption and fit, some of them have an absorbent material on the back (like terry cloth) to wipe the sweat from your forehead and brows. Don't get gloves that have too much padding - they can result in an unnatural position on the handlebars and can actually cause compression of the nerves in your hands, and they can cause you to lose your "feel for the road".

Just in case the new better fitting gel-padded gloves don't make any difference, you may want to ask the LBS if they could help you with a basic fitting (seat up/down, fore/aft). In my experience, changing gloves never helped much in solving hand numbness - the solution has always been some sort of seat adjustment to take pressure (weight) off of my hands. The fact that you're getting numbness late in long rides, could indicate that your position on the bike is changing as you become fatigued and it's resulting in you leaning forward and putting more pressure on your hands. With my riding position dialed in correctly, the primary reason that I wear gloves is to prevent callouses.