The in-game suit may be debatable (In my opinion the MGS4 looks way better), but there's no contest when it comes to the face. MGS4's in-game model face looks better than Big Boss' on MGSV.
However, when it comes to the cinematic models, MGSV wins hands down.
Mgs4 snake looks like a porcelain doll face, whether in-game or in cinematics. His facial modeling, lighting, and shading looked much better in the initial MGS4 reveal before everything got downgraded to fit the ps3 specs. MGS5 BB's face actually looks human with more realistic skin creases in comparison, again in-game or in cinematics.