They're 8 points more and you get t5, the ability to move 12 and rapid fire, the abilit to shoot 24, re-roll misses....

You really don't need to upgrade (imo) one multi-melta on attack bike and MAYBE one metla gun... you're fast enough to just assault the vehicle...

Also, what is this 3+ invun save ? Is that from moving 24 ? How do you move 24 and can you still shoot on the turn you do that?