In that situation I would also choose Plate, because of the numerous benefits.
But real world it comes down to that kinda choice in some games. Tank and bulky? Or low health and great swiftness/versatility? (I'm kinda matching attack on both, because with the plate you have super strength, blade is essentially a light saber) If you could get yourself up to a physical peak like Szeth than I'd choose blade. But if I was just myself, and the Plate was easy to put on, I would choose Plate.
Overall I would probably do sword in real life because summoning a sword that can cut bullets in half would be freaking awesome. More cool factor than practically.