The relic weapons are currently third in line behind only Relic +1 and Allagan weapons. Allagan weapons and Relic +1 have comparable stats, damage, and delays, just different stats. I believe they are to be used interchangeably (to some extent).

Example: The Paladin Relic, Curtana +1, has the same stats as the Allagan Blade, but their Accuracy and Parry numbers are swapped. The Allagan Blade also has higher DPS (not like that makes a difference to PLD). So, in this case, if you're having a hard time hitting the monster, use Curtana +1, but if you're Accuracy is fine and you're worried about getting wailed on, use the Allagan Blade to block more attacks.

Make sense?