Like Phil, I have a slew of new and old Looks, know for fact that the FKS/Pivot 14 toe releases upward, was told that the 18 does also, but with a heavier spring so that it requires serious torque, usually beyond what we can produce with a hand test. OTOH, had also been told that the 18 does not allow upward, period. So fitted the one 18 I ever owned to a bench, got a crowbar under the boot, and some electrical tape to protect everything, it lifted nicely. This was pure up, and obviously no measurement of force. Perhaps since then it's been changed to horizontal only.
FWIW, I use the 14 FKS for Sl and GS racing, there's so much elasticity that I've never pre-released nor would I ever worry about it. In fact, one beauty of the binding is that you can set it a notch or two lower than any other brand and stay in just as well. Also have seen plenty of 14's - and some 12's - on strong skiers and coaches. If I were on the WC circuit and routinely handled 3-4G's in a rutted turn, sure, the 18. Otherwise more about psychic factors than real performance, IMO.
Edited by beyond - 2/18/13 at 7:50am