Well the L5 implant upgrades help Jack's biotics do a lot more damage, but they're expensive. I think they're well worth the cost, personally. They're stronger than the L3 implants and at least they don't cause headaches and schizophrenia like Kaiden's shitty L2 implants. I just wish you could get biotic amps like before, I had a Savant IX that let me toss geth troopers around like little ragdolls.