From what I understand, the speed stat is just what your max potential speed is. Depending on the situation, agility and acceleration can be more impactful to your overall quickness.
For example, say two players with the same speed but different agility levels are racing from center ice to the goal line and back. The player with higher agility is going to win the race due to being able to stop quicker before racing back.
As another example, say two players with the same speed but different acceleration levels are racing from center ice to the goal line. The player with the higher acceleration will win because that player is able to reach his max speed quicker and is thus able to breakaway from the other player.
Ping plays a factor as well, because a player with lower latency is going to have their data packets being sent back and forth between their router and the game server faster, meaning their inputs get processed by the game server before a player with higher ping. So, say two players are racing from center ice to the goal line and back. If both players press the necessary buttons to skate and turn back at the exact same time, the player with lower ping will win because that player's inputs are being processed faster by the game server.