Some builders are quoting looped returns others are not.
Ask them to quote it both ways, and then tell you which way they think is better, and why.
You don't mention it, but are they using rigid or flexible pipe? PVC or Poly? There can be BIG differences in costs.
IMHO. Looped will be cheaper, as there is less pipe going to the pad, and may not cause you any problems. BUT, (and that is a big but.) individually piped returns allow you much more flexibility in the future, especially if valves are put on each line, so that you can equalize flow. You don't say anything about wanting a pressure side cleaner now , but with looped you will need to run a new line later; with separate lines, you can just dedicate one existing line to cleaner use, valving down the flow to the other lines if need be to run it. Or, Swimming Gods forbid, you get a leak in a line ( what, termites eat flexible PVC but not rigid???); with a looped line you are out of circulation as you plug all of your returns to stop the leak, with separate lines you can isolate the leaking line and use the others while you rally the repair team. For a truly balanced loop system, I would think that it would need to have the loop supplied at several locations evenly spaced around it, or it is no different then a common header with separated runs( and no way to isolate them.) A hydraulic engineer could tell you if the length of runs, and the number of turns, valves, etc.. for your pool would make any performance difference, one way or the other, as I am no expert. Unless you want higher head pressures, I've heard that bigger pool piping is always better, though!
Pipe is rather inexpensive to put in the ground now, especially compared to trying to do it later!
Good Luck, and Best Wishes!!!