engine failure after rotation

Is the only advantage to the gear mod a better climb out after engine failure?
Why not just keep your gear down until your at a safe altitude?
Don’t you give up some speed in cruse?
Isn’t there more cabin noise in cruse?
Don’t the doors help keep your working parts up in the belly clean?
What is the cost of this mod?
Who dose this mod? Can your A & P do it?

Just some questions that might come up!
Thanks
Cj