Advice

Do you...like Faber that much to consider him? Well joking aside. I think it's based on preference honestly. Faber if support and secondary DPS while Rama is a monstrous crit servant though his NP gain due to hits is shit, but I mean you could count in your two hands the servants having 100% crit damage modifier and if I were to count let's Houzouin, Li Shuwen are the only ones I could think of and unlike the two he's specialized in buster crit and could absorb stars and if it weren't for Lancelot's ability to create stars of his own and his higher NP gain then he would fall off Rama and more than that it's also a matter of survivability and such Faber would just die in certain crit or if he gets focused on and is somewhat like Isakandar amazing with buffs, but weak when he doesn't.

Personally I'd say using both together is often a good option as Caesar is an excellent support for Rama with charisma, a solid crit buff, and tactics but if you really have to chose one or the other I'd say Rama.

Rama does substantially less NP damage(he does less even at equal NP level against non demons) and both have comparable NP gain but where Rama can really shine is on his first skill that makes him a crit monster raising crit star weight by a large amount and giving a massive 100% crit damage buff on a very short 4 turn cooldown. This used properly will let him get NP very quickly with crit arts cards and deal huge amounts of damage in combination with his charisma skill - 1.18*2*2 gives a great 4.72x damage multiplier for crits, if you lead the chain with a buster card that jumps to 7.08 or an estimated 18k damage with an arts card or 24.5k damage with a buster crit in a buster lead chain. Basically what I'm saying what he lacks in NP damage he more than makes up for with the ability to put out insane crit brave chains so long as you have a way to supply him stars.