which is quieter for drain?

[seagirl]

My 75 gal has a 2" bulhead in it, i will use durso, but was wondering what type of plumbing would make for the least amount of noise. here is a picture(not too good ) of my 2 options. it would be easier for me to use the flex tubing b/c i already have it and it's easier to route, but i can do the PVC if it will be better.

also i want to have the end of the return under water(in sump) so i don't get any splashing noise, do i need a hole above the water line to for air so it doesn't flush

thanks for any help