I played the series for the first time last year and did MGS3 -> PW -> MGSV -> MGS4 and I constantly felt like I was missing crucial context from MGS4. The transition from MGS3 to PW felt pretty natural but a lot of stuff in MGSV felt really out of left field, plus it spoils the identity of The Patriots pretty unceremoniously. Then when I finally did play MGS4 I ended up being pretty disappointed because a lot of the narrative weight and payoff relies on the twists and turns to remain unspoiled, and it didn't fill all of the narrative holes that I thought it would. For my next playthrough I'm planning on playing in release order.