Let me start off by saying I am not an attorney and I don't know enough about your situation for you to give my opinion to much weight.
Rezonings, variances and other entitlements can be tricky and the correct way to proceed depends on the locality. Even when you think you have won, you may not have. (Case in point: I actually have to appear as a witness in a rezoning appeal case on Monday.)
Anyway, if you have time and money than doing all 4 appraisals would cover all your bases but it may not be necessary. You may not have to do the 2 current zonings options depending on the situation.
Questions:
Did the city allow for increased density of the adjacent property that is being developed with the aid of their condemning a portion of your land?
Does your SSA formula give you a similar density to what the adjacent property is going to be developed as?
And finally, if the condemnation wasn't happening, how confident are you that your property would be allowed to develop according to the SSA formula?
These are very important questions. Politically, most council members do not want it to appear publicly that they are playing favorites. Especially when it comes to Eminent Domain.
If they really are using your land to increase the density and value of an adjacent development (even indirectly), you have a very strong argument that your parcel should be allowed that similar increased density and value as well.
Unless there is a blatant reason why your property should remain under its current zoning, I would pursue the negotiations with the higher density/value in mind.
Force the Council to say publicly "we aren't going to increase your property value and help you develop your property in the same way we helped your neighbor." They don't like to do that. ;]