Actually i'm thinking about getting his ex with the Dimensions's end tokens. Do you think it is worth it?
Paladin Cecil (when he gets his EX+) fits into parties much like Agrias, like a "Cornerstone" Support. He covers a lot of general ground, providing Healing, Brv Battery and some light defensive buffing on Aura to the party via his two abilities, and also becomes capible of inflicting an elemental weakness to Holy, and allowing the party to exploit it via AA. He can be very useful, especially with his powerful HP+ and Brv+ helping with his longevity. The only issue I have with him in terms of using an EX token, is that he shares a banner with FFXII bad guy and broken monster, Vayne, making the wait until his banner a much more useful investment. That guy is worth a pity on his own, so you'll likely get Cecil alongside him when the time comes.
Dark Knight Cecil is a nice DPS that raises his allies attack stats a bit with his Aura, and can deal a lot of damage, do a lot of on-demand launches (with battery to allies during them!!!) and get a lot of longevity from his EX providing ability recovery, but DOESN'T have an EX+ for a long time, and should be carefully invested in with that consideration. A lot of DPS without an EX+ get stonewalled by increasingly impenitrible CHAOS boss defence, so unless you just want him because he's fun and useful for regular content, I'd be careful investing.
Both are good, but both have important considerations for EX token spending. If you ask me, While Ignis is an interesting Support with strange and useful abilities, I would spend the Token getting his bannermate, Zack, since he's the real MVP by the time it comes up, and is also amazing as a DPS and a tank, and as a positive role model!
There are a ton of protags to choose from though, and the shop won't go away, so try to look up some future banners and see which character you want has a banner mate you don't care for, that'd Narrow it down much better!
If you'd rather buff out your party now, you can't go wrong with WoL or Ramza, both very useful characters even with Ramza having no EX+ right now. WoL is a powerful tank with a billion ability uses and a healing EX, and Ramza both buffs the party and has a unique debuff that slots with other debuffer quite nicely, and he effectively takes no turns most of the time because of how his HP+++ works, so even if he's not doing damage he's keeping the party effective!
Squall is also nice if you need a safe and effective damage option, his mix of powerful AoE damage and REALLY good single target EX+ helps bring enemies down fast and effectively, even in CHAOS, and especially against trash mobs in regular content!