Like most things in comedy, it depends on how good the songs are. However, I would rather have 2 mins of average dialogue than 2 min of an average song as the non-funny ones really do drag on.
I'm probably the ideal target as I've written a lot of songs for NewsRevue and Treason Show. However, I would rather shows didn't decide to always have 1 song per episode on pain of death, as for some reason every show that does this has episodes where the writers seem to have forgotten to add good lines for whole verses, or even at all - normally the idea has crept in that you can justify 2 mins of no good lines simply by dressing up, by doing something in the style of a famous band, or by one or two sight gags.
Flight of the Conchords, Boosh and Klang have all had songs that were brilliant...and bizarrely also some that I wouldn't dare submit to a school play. Based on series 2 vs series 1 of Conchords, I'd rather they scrapped the songs and wrote more dialogue, which I think is now their strength...