gps/sonar combo question

[BP Swing]

Can anyone tell me if there is a clear cut advantage of having a combo unit vs. 2 separate components? I already have a depth finder I like but I was thinking of upgrading my old b&W gps to a color one that accepts navionic chips. Im leaning toward a new gps. Am I missing something here by not getting the combo other than a much lighter wallet? Thanks BP