When I am going for a leak, it is all about efficiency. Proper urinals (the big stainless steel wall jobbies) allow better spacing and during congested times, more pissing per lineal metre.
Say you have four of the separate style ceramic urinals on a wall. Numbered 1 to 4. Guy A walks in and uses urinal 1. Guy B walks in and uses urinal 4. Guy C walks in and has to choose who he wants to be piss buddies with. With a trough, Guy A can be on the far left side, Guy B on the far right and Guy C comes in and squeezes a lemon equidistant between the two others. Everyone's a winner.
If it is super busy (concerts, beer fests etc), dignity and modesty goes out the window and guys can side up and fit more pisses per metre in. It is easy to fit at least two guys in the space that one ceramic urinal takes up.
There is a great urinal in the Regatta pub in Brisbane. It is a one way mirror to the outside covered eating and bar area. You walk into the bath room and piss on the window to the outside. A water flow passes over the window every minute or so to wash it off. It's a cracker!
I remember the mens room at one of the beer tents in Munich for Octoberfest. It was a big zigzag of wall-type urinals. Must have had over 100 lineal metres of trough. That could handle a lot of pissed pissers. And it needed to.
Forgot to answer the OP's question. I generally stand on the floor rather than the grate. Have been known to stand on the grate if there is a puddle of piss on the floor.