the only good use for DA is their fun purple buffy called reflect damage. but it hardly reflects anything so the purpley aura makes up for it in my books.
other than that their panther would be best used to keep the clan hall dorrs shut.
Actually I'd choose Da coz of shield masteries, shield stun, black panther (which was upgraded in c4 and does a hella lot of damage with beast ss), high pdef and high hp make it pretty tough in melee pvp. It'll beat any melee class apart from Destroyers. If you're lucky you might land hamstring on an archer and give em a bit of a go but that doesn't matter anyway, c5 will be good for tanks I think.
DA is realy fun class, challenging etc... Glad is pure DD.
BUT if i had to make the choice again now, i go for Glad, cause as a DA, and after 60, its a pain to lvl since you will probably want a party, and there is only 1 tank allowed in 1 party when the same party need plenty of DD.
Unless you find a clan where you are the only tank, it will be hard to lvl. You will often find yourself sitting at the hunt spot shouting "tank lfp" till one of the party got its tank leaving, and if they dont have a rep already :o .