you can use either, i belive "tehnichly" win10 requires less "min requirements" than 7.
but you can get 7 and up date at any time you want.
i like 10 better it supports more hardware on its own and has better conectivity ( maybe not better but easier)
and i really enjoy certain apps such as the netflix app (just one reason why i would never go back to win7 having acces to apps on a big screen is just superb.