Sequel to The Bourne Identity trilogy… I pose unto you a conundrum. A riddle, if you will. Sword versus Esper debating time.
The Ragnarok sword should be turned into the Lightbringer right away; there is no reason not to. The Lightbringer is the bestest most awesome sword in the game:
But, you can Steal the Ragnarok sword in the final battle so you can have both if you go with the Esper. This way, you could after the final battle end up with both the sword and the Esper - you know, for completion's sake. In fact, you can obtain unlimited amounts of Ragnarok swords, and there's only one chance to obtain the Esper.
The Ragnarok Esper teaches Ultima, which is far and away the best offensive spell in the game. It's non-elemental, barrier-piercing, multi-target and stronger than anything that's not tweaked so hard it's embarrassing. The Esper summon attack is pretty bad but does grant access to elusive items for the completionists out there.
But, the Paladin's Shield also teaches Ultima, and technically the Magicite Shard item also may summon Ragnarok to do the same job. And going through the same final battle over and over again is a hassle.
In the end? Sorry man, it depends. Want the best most awesome game in the world? Go with the Esper, since that'll only mean you'll have to fight through the final dungeon one more time to get a Ragnarok sword in addition to your Esper. If you, on the other hand, want little fuss but do want the best weapon in the game, take the sword.
Metamorphose is the attack performed by the Ragnarok Esper when summoned. For the 6 MP it costs, you really can't expect much from it; slim as the chances may be though, the Metamorphose's unique ability to turn opponents into items may prove useful.
Metamorphose doesn't take Death Protection into consideration, nor is the Hit Rate affected by Magic Evasion. Every monster has his own 'Metamorphose success change' bit. This is why combos like Stop/Metamorphose or even Vanish/Metamorphose don't guarantee a hit, though you might expect them to do just that.
There are two uses the Metamorphose can have for you. The first one is obtaining rare items in quantities hitherto not thought of. The other one is the fact it kills monsters in one hit without checking for Death Protection; it may very well be a successful monster slayer if you know what monsters to target.
First off, a list of rare items you can only get more of if you opt for the Esper (ignoring the small chance of using Setzer or Magicite Shard to get Ragnarok at random):
Other rare items that are hard to obtain and can be produced with Metamorphose:
These items can be morphed from the enemies listed below. Most enemies have a set of four items that can be won from Metamorphose, with equal distribution. That means if Metamorphose hits, you have a 25% chance of getting the item you want. However, due to the success bit mentioned above, there is a second factor, and that is the hit percentage of Metamorphose itself. For most monsters, that percentage is 12.5%; therefore, you can assume that unless mentioned specifically below, the chance of getting the item you want with any given summoning of Ragnarok is a lowly 3.125%.
Now, there's also the issue of Metamorphose being an attack that sets Death and doesn't respect instant death immunity whatsoever. So here's a list of monsters that are immune to instant death but have a Morph Hit Rate equal or superior to 50%:
Out of those, the only really spectacular one is Brachiosaur; the strongest random encounter in the game has an immediate 50% chance of falling without a fight if you summon Ragnarok. 99% isn't entirely accurate in this list; it's actually 99.609375% (in other words, there's a 1/256 chance it'll miss).
The eight elemental dragons (as well as Proto Armor) all carry a 12.5% chance of a successful Metamorphose attack for a piece of Crystal equipment (Crystal Sword, Crystal Shield, Crystal Helm, Crystal Mail).
There you go, if you don't think those odds are too bad, go nuts, kiddos.