Pentax 70mm Ltd or Sigma 70mm or Tamron 90mm?

Been watching the forum for a while now and read some web reviews on the lenses mentioned, but looking for advice if one is ultimately superior than the other in terms of image. Or is it the case in the real world, there isn't that much of a difference? I would like to buy a lens for portrait photography(new or mint secondhand within my budget.) Any help from all of you more experienced than I would be appreciated.

The 70ltd is a superb piece of glass, as a portrait lens it's faultless. The other 2 are macro's and as such have a very close focusing distance but would perform just as good for portrait work. I'd go with which ever one you can find for the money you have

The 70ltd is good value at the moment IMO, and for portraits I'd go for that one as it's a shade faster than the other two. But any of these would be excellent; it comes down to whether you also need a macro.