buck converter to USB or Vin on Nano?

I'm stepping down 15V for a Nano with a buck converter. Am I better off stepping down to 7V or so into Vin or down to 5V into the USB jack or the 5V pin?

Thanks!

Step down to 5 volt directly. Why create power losses in the inbuilt 5 volt converter?

Railroader:
Step down to 5 volt directly. Why create power losses in the inbuilt 5 volt converter?

makes sense to me, why force the arduino to reduce the voltage. I assume I can feed the 5V pin from the converter and still power other things from that same pin?

Yes, as much as the bucl converter can supply.