Is there a difference between pseudo-ephedrine hydrochloride and pseudo-ephedrine sulfate?

None: Both are systemic nasal decongestants. They are different forms (actually, different salts) of the same drug. They have different molecular weights. Pseudoephedrine hydrochloride is sold under the brand name sudafed. I'm not sure if the sulfate form is available anymore. For details, see: http://www.Drugs.Com/mmx/pseudoephedrine-sulfate.Html.