To be fair it really just depends on how they handle things. Crimson's curse of being undying could in the end have the exact same effect of Ragna's, as in all the people he meets are without a doubt going to die, even if only because of age, while he will live on.
Ragna's curse on the other hand is more "direct", but supposedly he could end his suffering by killing himself, since he shouldn't be immortal per se. Of course he's not going to do it, but in a way you could say he's just willingly prolonging his own anguish by being "stubborn" in his wish for revenge.