They are not the same though. As has been discussed ad nauseam, player generally are going to be more committed to a group when they cannot hide behind the shelter of anonymity that x-realm LFD provides. If your reputation as a player and future grouping ability is at stake, you are far more likely to stick with your group through thick and thin in order to not run the risk of being label as a bad apple. LFD provides a too-convenient cop out, where both bad play and rude, immature behavior is not penalized; all the player has to do is click the little que button again and he is given a fresh group in which he can continue his bad play. Imo this does affect the difficulty; since players have no reputation at stake in a LFD dungeon their is very little stopping them from leaving at the first sign of struggle in the group. In order to stop groups from constantly falling apart, the solution has been to simply nerf everything to the point where its almost impossible to struggle. I'm not saying it has to be that way, but the entire point of this thread is to point out that WoW, despite the "incredible success" of the LFD tool, seems to be going back to premade groups for their challenging content. That to me is very telling in regards to the question of 'can LFD content be challenging'.