I`ve Lib DarkSeries & vans aura boots. Now I want one of the Union bindings. They need for slalom, freeride & pow( I so old for freestyle - no more jumps).
the 2012 Contact had better toe strap, without perforation - but 2012 Force had strong highback.
Please HELP ME!
If those are the only options, then I would say go with the Forces - stiffer and much more responsive binding. Really no point putting Contacts or Contact Pros on a stiff, aggressive board like the Dark Series.
Side note: Vans Auras are a slight odd choice for the type of riding that you are describing.
I'd go with the SL if you're looking for a stiff Union binding. Otherwise, between the two, I'd go with the Force. Or, if you're in no hurry, and budget is not a concern, then you can get the 2013 Union Charger when it comes out. That will be the stiffest binding Union makes at that point.
The Contact is a softer flexing park binding. Not the best for freeride really. The Force is what Union considers to be their all-mountain freestyle binding. I believe the toe strap on the 2013 Rome Targas will be much better than the old one. I've seen the prototype, and it's well made.