Oooh! Beatles vs. U2!
First, compare the proper eras of both bands. Yes, in the same time frame, the Beatles clearly recorded a lot more. However, U2 has toured tons more, so it balances out. Also, the 60's, even for a successful band, vs. the 90's for a successful band are not the same. Once success is established, one doesn't need an album every year or two - quality is definitely expected by fans over quantity.
So if one compares simple tunes like "She Loves You" to any era from U2, it also has to be to early U2 songs like "Boy/Girl". Also, the Beatles were trying to get estabilished in an era of other bubblegum pop, while U2 was coming from a punk-inspired route. So the comparisons aren't exact, but close enough. IMO, both are the same.
As the Beatles advanced, so did U2. The Beates' lyrics turned more introspective early on (with songs like "Nowhere Man") while U2 branched out to explore God and religious themes/imagery. Both bands explored political justice.
The more experimental aspects are too subjective. Some of the more "out there" Beatles material is as questionable as some of the more "out there" U2 material.
So the careers of both bands are too similar to me to truly say that differ (other than length and touring). Near the end of the Beatles, they had similar sounds to their mid-60's era, just as U2 now has similar sounds to their late 80's/early 90's era. Had the Beatles continued, it would have been interesting to see what was next. Based on their various solo careers, I feel it would have been a mesh, with the pop of Ringo Starr, the early great stuff from the Wings, the continued political side of Lennon and the soulful side of Harrison. I have a feeling this is a clue as to what we'll see next from U2 as well - that is, not something so revolutionary any more, as they've done that, but something that expresses all 4 members' tastes, yet retains some of that pop sound, while being relevant. I do not think we'll see another shift as we did from "War" to UF or from R&H to AB.