It has 10 less attack points than the Zodiac Spear, so in terms of damage in a single strike, it rivals it, although it is slightly slower regarding it's charging time.

I think if you have Zodiac Spear and Masamune + Genji Gloves, your party could decimate anything with an orange HP bar on Ivalice, and that Tournesol is something for those who "missed" Zodiac Spear (i.e. don't have the patience to wait out a 1/1000 chance). But hey, I've got Zodiac Spear and Masamune + Genji Gloves, and I've spent the last 4 in-game hours gathering the required loot for the Tournesol, so I'm hardly one to talk

I just like collecting things. =]