With a logistic model, the difference of LS-means as provided by the LSMEANS / DIFF statement is a difference in log odds, or log odds ratio. If you particularly need the difference in means, then that is a nonlinear combination of model parameters which can only be done using the NLEstimate macro. You will have to determine the proper function to estimate based on your model. See this example which shows estimating a difference in probabilities from a logistic model. It uses a model in PROC LOGISTIC, but the same should still apply to a model from SURVEYLOGISTIC.