Jaffar or Felicia, and how to go about it?

They can both do some serious damage to the enemy, but in different ways. Jaffar can inflict some heavy AoE chip damage while Felicia can deal some devastating blows to units, especially with Glacies.

As far as which to refine, that's really up to who you use more, or who you find more interesting. Felicia's Plate doesn't really "need" the refine if we're being totally honest. The added speed and resistance is really nice, and the charging effect against mages is extremely handy, but many will say that Jaffar isn't really "that great" of a unit.

I'd probably go with Jaffar. I find them both interesting (especially when Felicia can take out units with Glacies), but the massive AoE chip damage is extremely satisfying in my opinion.

Felicia doesn't need the refine that badly, because she's already good enough with her base weapon. Divine dew is so rare, that it would be a waste to put it just into a small stat boost or a minor effect.

With that said, Jaffar's upgrade not only gives you that chosen effect, but he also gets the 10 aoe dmg, which he doesn't have with his base dagger. I'd go with the sweep upgrade.

thats the same IVs as my Jaffar and hes really decent and if you run a close counter vantage build on him, hes gonna serve you really well especially since he can get free chip damage with his weapon refined for effect.

deathly dagger's refine effect is too good to pass up on so if you're not into close counter on him, another good idea would be windsweep and the phantom speed seal. you'll lose 7 points of free damage with every initiation but it shouldn't really matter with a dancer on your team