I am not sure how tough this is.
INXS was a decent but (IMO) forgettable New Wave band from the 80's who produced one true "hit" and a few decent songs.
U2 is Ireland's greatest contribution to rock music, and have not only influenced other bands, but also politicans, people, voters, etc. U2's music is so deep and complex, they try so many different styles and sounds, and when they want to be political, they hit hard and don't look back.
Compare "Hold Me, Thrill Me, Kiss Me, Kill Me" to "New Year's Day." You'd almost think the songs were from different artists. Both were hit singles from U2, but each had a totally unique sound,
Now look at "She Moves in Mysterious Ways" and "Sunday, Bloody Sunday." Again, two totally opposite sides of the musical spectrum, but both worthy hit singles. Phenominal.
Also, after their run in the 80's INXS largely disappeared. U2 has hung around an is STILL putting out #1 records and songs in 2007. Vertigo was a HUGE hit in the US, and their collaboration with a resurging Green Day on "The Saints are Coming" was epic.
U2 in a LANDSLIDE.