The latter is great, albeit a bit short for the main operation. That being said, it is supposed to be the "Tanker" chapter to the main MGSV storyline (think back to MGS2, Tanker was ~1-2 hours, then there was the main game with Raiden).
I know. But I still wanted to enjoy a new installment of Metal Gear Solid, as I don't have ps3 and still haven't played the MGS4 though.. But I have finished MGS 2&3 on my PS2 multiple times and enjoyed it every time