This is the most informative post in here.
Everyone else who is looking at ATK stats, NP levels, etc. and try to base their judgement off that - don’t. ATK stat and NP multiplier are just two of half a dozen variables that determine final damage output. You need to always refer to an actual NP damage table rather than looking at these things individually, or else you can thoroughly misjudge the actual damage output.
At NP3 or lower, NP1 Jeanne still beats Mordred E/: made a mistake, NP3 Mo and NP1 Jeanne are near equal with Mordred having a negligible edge of 200 average damage, and NP2 Jeanne blows Mordred out of the water (heh) at any NP level.
Now, with that out of the way; as others have said, Mordred has an easier time refunding and thanks to the NP4, also a slight edge in damage.
However, since you happen to have Nero Bride, Jeanne has one massive advantage over Mordred. Her 40% battery allows her to run with a double Nero Bride + tamamo setup without any restrictions on her equipped CE. This means 2 things:
- Jeanne can run any event CE and thus even do 6 slot setup loops; this is massive for lotteries and other events where high drop bonus gives you a significant farming edge.
- Jeanne can equip Black Grail and absolutely annihilate Mordred’s NP damage even in an NP1 Jeanne vs NP5 Mordred situation, at the same drop bonus.
In order for Mordred to reach 100% charge to shoot off her first NP, without any starting gauge CE, you are forced to run Waver, which means a sharp decrease in both refund and damage output compared to Bride or Tamamo. Compared to Paracelsus, it will likely be slightly more damage, but also significantly worse refund.
There are some caveats to keep in mind here:
- Jeanne can only run this CE-less setup once Nero Bride has had her upgrade that gives her the needed 30% battery. This upgrade is still a year away on NA.
- All of these considerations are for stable setups, e.g. setups where the refund is guaranteed no matter the enemy. Mordred will still be able to run CE-less in some quests as well even by taking the penalty of less refund through needing a Waver, provided she’s up against Casters or Riders who provide higher refund (especially since she’s a Rider herself, so you’d mostly bring her vs Casters anyway), or because of overkill damage increasing the refund. But that will require some trial and error for this specific quest, whereas CE-less Jeanne works literally anywhere as long as wave 1 and 2 have 3 enemies (the basic requirement for any sort of AoE looping).
Now, with all that in mind, I still wouldn’t consider Jeanne enough of an improvement over Mordred to warrant rolling for her if you already have Mordred at an NP level above NP1. You might be better off diverting your Jeanne funds to Dantes instead if you manage to roll Skadi.
All of this is only with gameplay considerations in mind, of course. For character preferences, you’ll have to decide for yourself.