Well... They aren't really all that comparable because they are so different. Glengarry is a fast, special sweeper. Doublade is a slow physical beast, somewhat weak to special with a potentially awesome ability (no guard is incredible with certain low accuracy tm/egg moves)... Aegislash loses "no guard" but is a beast. It's only weakness is speed, but it's basic strategy (king shield, attack, king shield, attack, etc) actually counts on it going second. One of the only ways to effectively counter aegislash is to have a month at is slow enough to catch it in its offensive stance. That being said, it's almost guaranteed that aegislash will eventually be banned competitively so if you want to do competion stick with eviolite doublade.... Frankly I like doublade better. Both are hard counters to fairy, but in my experience most fairies carry a psychic attack in online battles, which makes doublade better. As far as special sweepers go... Gengar is good but you can do better. You can also make a much better choice for your mega stone mon. If you do go with Gengar be sure to give him sludge bomb or sludge wave to get some STAB action on those fairy types.