I'd agree with most folks here, that Bobby wrote more complex chord changes. That said I think the vast majority of what Jerry wrote was simple, be it chords or melody. Aside from a few obvious exceptions like H>S>FT or Terrapin, or the previously mentioned Crazy Fingers, Jerry was a pretty straight forward composer, which I think comes from his strong folk roots. Where JG's complexity came in was in his solos & improvisations, regardless of who wrote the song Bobby, Phil or the man himself.
I think some of his most memorable melodies are some of the most simple, Black Peter or the intro melody of BEW or Bird Song, NSB, Loser, TLEO, etc. None of these songs are overly complex in melody or chord structure. Again where the complexity comes in is in the improvistation. This may start some shit, but it's just my opinion.
Goin' home, goin' home
By the waterside I will rest my bones
Listen to the river sing sweet songs
To rock my soul