Both dramas are filled with countless troupes and cliches, both share the crossdressing and cohabitation tags. Although, My Unicorn Girl has a higher budget, if you are a sucker for troupes and dramas that kinda parodying them, then you can try the other out.

male leads are very similar: popular, smart, cold, doesn't say much, but can be tender
female lead similar: little naive, chasing after male

the relationship dynamic is very similar, but in MNCS the male lead is not as cold.
they both "live" together, in MNCS they dont live together but are neighbours

The childhood "friend"ships, and featuring cute end clips of them in their childhood interactions.
FFMW has MMA, while SIL has ice skating related sports
male leads love sport are kinda dorky
female leads are very confident and sassy

Has very similar vibes of light hearted and university life
Both male leads are very popular in their university and are kinda dorks
Both female leads are very confident, witty and bright

Has the same leads, so if you cant get enough of the chemistry you can give pleasantly surprised ago