Replying to Fks 180 vs. fks 140?

first off i realize that the din ranges on these bindings are different and that they have different toe pieces. my question is whether it is worth the extra $100 for the 180s and whether the vertical toe release on the 140s really does anything to save your knees. I'm 6'1" 180 lbs and usually ride with my bindings set at 9 or 10. These are gonna go on my park skis. i currently ride with fks's that have a vertical toe release but ive only have it pop up a couple of times.