I actually have both kinds of lanolin on hand, but I've only used them in lip balms so far, which makes for an awesome lip balm, by the way. For what its worth, both behave the same and feel the same in my balm. The liquid kind that I have is from the health-food store and is made by the NOW company. The semi-solid lanolin that I have is made by Lansinoh, which is a pure, hypoallergenic lanolin.
I personally would have no qualms about using either one in soap, and have actually been meaning to try it specifically in shave soap, but I just haven't done it yet. I am going to be using it at 5%, as part of the actual oils amount.
For either one, I would use the SAP listed on SoapCalc for lanolin liquid wax: The NaOH SAP# is .076, and the KOH SAP# is .106.