To learn what your core difference is, talk with your clients.
Client interviews can reveal some very useful insights. For example, asking your recent clients (who presumably know your competitors) “Why did you choose our firm?” and, “If we didn’t exist, which firm or provider would you go with? Why?”.
That will tell you a) who your competition is, b) what their competitive position is and, c) why yours is more attractive. Pretty powerful information!
Learning what clients find attractive . . . makes you more likely to attract them.