Ferro-Lamellor seems better to me for the reasons recently clarified above. The weapon systems that it effectively neuters are some of the most dangerous in the game. Not only do LB-X weapons do no damage, but SRMS and RAC-2s both get de-fanged by this armor just by removing that first point of damage. A streak-6 isn't so painful when it is a total of 6 damage spread across your mech.
Also, the +1 PSR for hardened armor is a pretty serious issue. I played against it a lot after the TRO 3145FS came out and realized that unless you have an elite pilot, they really do spend a lot of time on their heinies. A friend of mine loved the Hitotsume-Kozo and would bring it to every lance on lance fight we did for about a week. Through focus fire, once I "dumped" his favorite toy, I'd just put 20-40 damage into every round, and his pilot would either stay down or go back down.
Piloting 5 + 2 (40 points damage) + 1 (hardened armor) + 0 (medium weight mech)=8 required for the PSR roll. So I'd dump his favorite new toy, and then normally luck would have it and it would fall down at least one more time on its own accord.
Now could I do this if it was equipped with Ferro-Lamellor? Sure. But, the extra 1 point PSR penalty (for Hardened Armor) is very helpful when it comes time for my friend to be making the roll to stand up (and failing).
My experience with Hardened Armor is that it looks scary and its easy to be daunted by a mech like the Shiro or Hitotsume Kozo. However, after 10+ matches, it seems like the drawbacks to Hardened Armor during gameplay really bring it back down to earth. The drawbacks to Ferro-Lamellor only take place when you need to have enough crit space.
If I had the choice, I'd go F-L every time unless I knew I had the spare BV to put a kick-butt pilot in the mech with Hardened Armor. A 2/3 pilot in a Hitotsume-Kozo or Shiro would be a scary, scary thing.