Pentaxor, there are sadly no FA 135mm lenses readily available on the used market where I am. Not so easy to find but I got mine from China. This is why I wish Pentax would roll out an all new modern version both in f/1.8 and f/2.8 maximum aperture, preferably with WR.
As to the respective arguments about build quality, it really depends on the condition of the lens you have. For the out of production FA 135mm, the only copies circulating now would be used. Being an AF lens, the focus ring if used manually isn't as well damped and the focusing cam can sound scratchy like many FA lenses. In this respect the DA* lenses do have the edge but I won't consider the FA 135mm's build quality to be cheap or inferior, just different. About the only thing I don't like about it is the built-in plastic hood. It may have been fine during the film era but on digital it is just too short. Mine was stuck as the internal O-ring to click into place when extended was dislodged and was sent back to Japan for service. Came back perfect.
There is a lot to like about the FA 135mm. It is very compact and being an internal focus design, the lens barrel does not extend when focusing and it just beats the DA*'s SDM in terms of speed, probably one of the fastest AF lens Pentax ever made. Of course the DA*'s noiseless SDM will have the edge in situations like concerts where you don't want to disturb others but it is big enough lens to get noticed, unlike the smaller FA which is ideal for street shooting and outdoor portraits.
Like other FA lenses, PF is there at wider apertures but not terribly serious, this issue is also evident on the DA*. Flare is well handled on the FA 135mm in spite of the short hood but veiling flare is more an issue with the DA* 50-135mm. I think if one uses the FA or DA* lenses in bright light there is little to choose from but for shots at night with small pointed lights sources, being a prime, I feel the FA has the edge. Bokeh wise both are nice but this is rather subjective an issue and depends a lot on the background.