My Army EOL training used both pavement and unpaved landing areas....but the standard was the same....one skid length ground slide maximum to receive a passing grade on the maneuver.
Later on in the final stages of our training we did have contests on who could slide the furtherest which made for some good fun and some soiled undies!
But then we did lots...lots....lots. and lots of EOL's and simulated tail rotor failures along with the more mundane things as we were all headed off to where we would get to do them for real with some frequency.
So...pick your poison....asphalt or sod....just avoid the mud and big rocks.
Out in No Where Texas we also had to look out for the Rattlesnakes.