I've used the poly FSS trigger for about a year. I just changed my trigger to the new Flat Faced trigger and it's only available in aluminum at this time. Installing the pin into the trigger bar is a bit more fussy, in fact trying to tap it in with a hammer wasn't working. I had to press the pin into place with a bench vice. After that was done, no problem. Honestly I don't know if there is much difference between the two, I couldn't notice any flex with the poly trigger, both the triggers are smoothed out nicely and finished in black so from an appearance and feel aspect, they are pretty much the same. I do like the operation of the new flat faced trigger a lot more than the curved FSS trigger but it has nothing to do with the material (AFIK). I think they come out with the aluminum versions first because they can be machined out of billet stock and changes can be made easily. The polymer triggers require an investment die and are quite a bit more of an investment, especially if changes are made to the design. Hope this is helpful.