The difference between Yu and Ren in their respective games is day and night

For example:

• Yu is considered very popular & the big man on campus at school while Ren is considered very infamous & an outcast / loner at school

• Yu is overall treated as pretty handsome while Ren normally is treated as pretty average / plain looking at best.

• Yu is one of the more mature & straight-man members of the Investigation Team while Ren is one of the more carefree / laid-back & goofier members of the Phantom Thieves

• Yu is more involved in extracurricular activities at school while Ren straight up doesn’t join any extracurricular activities or shows no interest to join one and does more of his activities outside of school.

• Yu wears his school uniform open & resembles an Bancho, but his personality is kind & well-mannered. Meanwhile, Ren wears his school uniform prim & proper but his personality is rebellious & free-spirited

• Yu’s design was meant to resembles an loyal & sincere dog while Ren was meant to resembles an polished & alluring black panther who has two faces: one that he hides and one that he shows to the public.

There’s probably plenty other examples ( and if anyone can think of more feel free to mention them ), but you get the point.