Well, I think Beregond is the best defender in the game. One does not need think long to conclude that, he has the highest defence strength. However, there are other values. Elrohir or (Tactics) Boromir can defend multiple times without attachments, the mechanism of the latter seems more potent - and economical, the former has higher defence strength. Then, Elrond has the same defence and is Lore which allows for the immediate play of A Burning Brand, with shadow effects ever more deadly that seems a distinc advantage. Coming back to Beregond though, it is not guaranteed to have a shadow cancelation on round 1 where the attacks will often come, Beregond cannot defend multiple attacks as the above or Beorn (who can also take many hits despite having low defence) but his highest initial defence to date is a good safety cushion. Finally, the direct damage is very powerful tool in dealing with both enemies' attacks and their shadow effects, Spear of the Citadel plays for free on Beregond and combined with the cards like Goblin-Cleaver which can then be played too, can defeat many enemies without ever attacking them.