Usually a compact (34/50) paired with something like 12-34 is plenty. I use a 34/28 to tackle all of my climbs. My hardest only being 15% for half mile. I used to do it on a 34/25, and that was pretty difficult. Most people don't do 10% climbs, and most don't have the opportunity to. There is a climb I love, its 9% for 3.5 miles, and only 22 have done it. There is a 3% climb for 6 miles, and almost 300 people have done it. This being in the same city, like 10 miles apart.