There are 4 big resons i think Sam Ramai chose to have Harry wear a new suit.
1) Harry is prabaly more comfortable, more flexable, allows him to have weapons on himself.
2)Harrys glider looks a lot faster than the onw his father had, reasons is if you remember last fight with GG in Spider-man 1, Peter's spider sences worked when when glider came up behind, but if you read the fight scene that was shown at the Sony Convention Center, Peter was riding his little motorcycle Harry came and swooped him up from his bike.
3)His weapons seem to look very cool. He has a he has one of those wristblades on his right arm, his has a sword on him( not on the glider ), he has the GG boms and the razor bats. To me all these weapons make him more lethal and makes the fight sequences much more intense.
4) And i dont want to remember that Harry and Norman were both Green Goblins cuz i think Norman was a psycho all he wanted to do scare people and bring chaos. Harry just wants Peter to die. And I love how they made the GG suit in the first one because it looked all scary. ANd i loved how the suit totally describes what kind of a person Norman is.