Center mounted skis are better for spinning and jibbing, basically because you are perfectly balanced between the tip and tail. When you center mount, however, I would reccomend two things:
1. ALWAYS measure yourself. put your ski on a table and put somthing on top of it to decamber it (make it flat). Then, mark right where the edge first lifts off the surface you have it on, and do the same for the tail. Then get a piece of string, and cut it as long as it is between those two marks. Fold the string in half, make a mark in the middle, then string it back up between the 2 marks, and you will find the true center.
you only have to do this for one ski, then you can use the mark you made and the recomended mounting marks on the ski to measure the distance forward and mark if with a ruler for the second ski. This way it's consistant.
*The reason why I say to do this is because most shops don't have a clue, and will mount your ski in the middle based on the very tip of the tip and the very tip of the tail, and with most skis this will result in a ski that is actually mounted more forward than in the middle or back.
2. Although many will disagree, NEVER get your skis mounted right on top of the middle of the ski. They ski great on rails and air, but they will not be fun elsewhere. give it about a cm back from true center. It doesn't sacrifice anything in the park, but it will make the ski perform much better out of it. Trust me, the extra CM makes a difference. if you look on the new Armada site, you will see that the pros don't even mount dead center.
Traditional mount is for traditional skiing. I will never mount a ski there again. All my park skis are a cm back from center, and my powder/all around skis are about 4 back from center. If you are into spinning on any feature, cliff, park table, etc, I would suggest mounting forward.