I play a lot of hockey and being able to have your legs through 3 periods is very important. Working your legs for strength probably will provide you with endurance to last all 3 periods. Having upper body strength also will help you in front of the net and in the corners. You have to be able to skate, so that makes your legs most important, but having upper body strength is also important. So pretty much just do what you feel will be the best for you. Also I've heard an announcer say that Joe Sakic works his legs on the day of games. He says that it helps him keep his legs for the entire season, so this is something to look into.