^what he said. But if you just want to know anyways....
A center or true center mount will put your body mass above the sweet spot of the ski (center), giving you more tail if you're backseat a lot/making sliding rails easier and most everything else in the park
A rearward or back mount is what I would recomend for skiing groomers and powder. You have less tail (so if you're backseat a lot it doesn't help), and is NOT RECOMENDED FOR PARK.
You can also do a progressive mount. All i can really help you out on for this mount is a know its used more by female skiers, and puts your mass in front of the sweet spot (center of the ski).
You can make minor incraments in between these 3 major mount position, but a lot of this really comes down to what ski you're riding/what you're comfortable on and what and where you are skiing.
If ya got any questions about this just PM me.
Ok a true center is obviously in the exact middle of the ski, so if you're probably landing switch a lot and skiing park quite frequently on these thats a recomendation. where as a normal center mount is a litle farther back, this really is still a "park mount" but limits you're balance while riding switch and stuff, however, gives less of a feel of the tail. All in all i would go with a true center mount (since you said u will be snowboarding most of the stuff outside of park), because a true center mount only gives benefits (for park).
Please corect me if im wrong about anything i said, agian I'm not an expert.