This is what Bill Flanagan said about U2's process of making their songs, i think you'll find it pretty interesting regarding this topic, and i think it will answer any question about Larry's abilities and his contributions, as well as the other members' role:
-----------------------------
"It is fair to say that Bono writes most of U2's lyrics, but he does not write them all. Edge has come up with more of U2's signature riffs than any of the other three, but the other three have all written plenty. I've watched U2 compose and record. What surprised me was how they switched roles depending on who was feeling inspired. Listening to a playback, Larry came up with an idea for a new melody and sang it to Bono, who tried it on the track. When Bono left for the night, Edge took over writing lyrics. When Larry left the room, Edge sat down behind the drums and put down a beat for a demo. Adam picked up Edge's guitar and suggested some chords. The four members of U2 have been a band since they were schoolboys; they taught each other to write and play. It is almost impossible for an outsider to tell where one leaves off and the next begins. The songs truly come from all four of them.
What impressed me in watching how U2 write was their willingness to change direction in a moment and follow the music wherever it led them. They could be working on a song for days and have it just about done, when suddenly Adam would try a different bass lick, Larry would switch his drum beat around to go with it, Bono would get an idea for a new lyric and - fast as that - they were gone, the almost finished song abandoned while U2 chased down a new one. I have never seen songwriters less worried about nailing a song down and being done with it. They seemed to delight in the creation itself, and not worry much about running out of ideas. "
------------------------------------
