I'm not going to pick a side, that said, these are my humble observations.
S15: Its pretty not beautiful, parts are plentiful and affordable, handling is great and safe, spacious compared to the FD, power potential is respectable, power delivery is predictable, comfortable and user friendly, fuel consumption is pretty good for a turbo car, every tom, dick and harry mechanic can service it.
FD: Its gorgeous, parts are getting pricier and rare, handling is beyond what most other red cars can dream off, crammed and not for the claustrophobic, power potential is amazing, power delivery is awe inspiring, revs like no tomorrow, sounds like a bat outta hell, uncomfortable, impractical, beginners need not apply kind of feel and handling, 50 - 50 weight balance, delicate, horrendous fule consumption, no one can fix this b*&ch.
Conclusion:
Nope, I'm not going to pick a side but I am going to summarize the cars' attributes and draw analogies.
S15: A sweet girl who's easy to maintain and responds well to love. She's practical and is eager to please. Looks pretty good when dressed up and loyal as hell. Boring after a while
FD: A mistress who's drop dead gorgeous whether dressed up or in the raw, temperament of a B&*ch, has to be spoilt all the time, high maintenance, Horny as hell and just wants to F&^k all the time. Not happy when neglected, kinky and naughty, vicious. Every boy's wet dream.
Go figure