Also remember that if you go the spell way, you are likely to run up against first law issues. I'm a player in Luminos' seattle game and I've got a rote spell that summons a sword (Conjuration at Evocation Speed through use of Soulfire), and I am not allowed to kill mortals with it. Also, remember, if you go the conjuration method, you are summoning a sword. So it should deal damage as a sword. No weapon 7 sword that lasts a bunch of exchanges, more like a weapon 3 sword which lasts all scene.
Here is my rote spell, remember, i've got soulfire so Im allowed to use a conjuration effect from thaumaturgy at evocation speed.
Xífos to̱n Ouranó̱n Sword of the Heavens
This spell uses the power of Soulfire to forge a blade with the Spirit of the caster.
Type: Thaumaturgy, Conjuration
Complexity: 5 Shifts
Duration: One Scene, could be longer (until the Sun rises), but its supposed to be something you call from nothingness not have on you at all times.
Effect: This conjures a blade of pure spirit from the creator's soul, it has a weapon rating of 3. It is made of soulfire, and is thus a very powerful weapon indeed. It satisfies any Catch requiring a Holy source of stress, and it downgrades one rank of toughness (From Mythic to Supernatural, from Supernatural to Inhuman, and so on).
Description: Motes of Light gather in a pillar growing out of the casters closed fist, becoming solid and more real. The motes flare a searingly white light, and a chime of metal issues forth from the newly created blade. The sword appears to be made of molten silver, which shifts and flows while still maintaining its shape.
Also, I have had this thing dispelled once, just remember its a possibility that somebody will counterspell it.