I've worked as a Project Manager/Estimator in the commercial tile and stone industry for 25 years. Email me if you have any questions.
Your choice of adhesive should be based upon the type of tile or stone you are installing and the substrate it will be installed over.
SpectraSet appears to be marketed to the homeowner market. Not one I've seen before. It is polymer modified and meets ANSI 118.4 so is a resonable choice of adhesive for use over concrete, plywood or tile backer boards. It should not be isntalled over OSB or particle board.
http://laticrete.com/Portals/0/datasheets/lds6860.pdf