There's nothing wrong with comparing them since they do pretty much the same roles, targeted burst gen to help slower kamis keep up. Saras does her job well enough imo, but Titania has the ability to push your team beyond "good enough" by reliably turning even the slowest of kami into a speed monster every burst round (her two buff is enough to guarantee 90 BG in 3 turns or can be split to help 2 different kamis keep up). You really just need 1 reliably fast (usually cu) other hime, and suddenly your team is in overdrive. As much as I like Saras, she just can't carry a team like that because her CDs are too long for it.
That said, if we're really comparing buffs/buffers... shouldn't we also be talking about the 800lb gorilla in the room that is Tishtrya? Talk about good effect/CDs.