If you look at Photozone's review of the DA 70 and FA 77(
Pentax SMC-DA 70mm f/2.4 Limited - Review / Test Report), Klaus really comes down on the line. Seems to indicate that the DA 70 is sharper edge to edge, faster focusing and with less purple fringing, but also with less wide aperture and bokeh not as good. I think that if you compare the FA limiteds to the DA limiteds, you will find this to be similar across the board.
For me, the thing that pushed me towards the DA limiteds is a combination of cheapness, size and the new adjustments that are made in the K7. They are definitely excellent, very sharp, contrasty lenses.
Others have decided in the opposite way, to go for the wider apertured FA limiteds. Both are excellent, but at the same time different.
On the subject of Tokina/Pentax, I don't think anyone fully understands this relationship. They definitely design some lenses together -- the DA *16-50, DA* 50-135, and DA 12-24 are all examples. Tokina does not release any of their lenses in a K Mount. That said, none of the limiteds (except for the DA 35) are available from Tokina in any mount. Seems like those are Pentax's baby all the way and one of the things that makes the K Mount special.