Often, fish stores will not sell the females of Gourami species because they are drab in comparison with the males. (A good way, also, to make sure that fish stores will continue to buy more Gouramis, if the fish stores and clients cannot mate the gouramis!) Which brings me to the question of what they do with all the superfluous female fry......... a question that has been bugging me seriously for quite some while!!!
The dorsal fin is the official marker for the dwarf gourami species (male's is pointed, female's is rounded), but I'm not sure about other gouramis. Chances are, lmw80, that you just have two males with slightly different dorsal fins (often in the stores the dorsal fins look different because they are nipped, or because the fish is not fully extending the dorsal spines upwards). Is there a difference in coloration between your two specimens??? That's probably a better marker than the dorsal fin.