I was training a co-worker to weld. The arc hurt his eyes with a 10 glass. The 12 glass didn't help so he bought a 14. After a double pass, pretty weld, I taped it with a hammer and snaped his weld.
I used a 4 to 10 on different jobs. One pass on must jobs. Not much welding since '08. The hardest things I try now are thin metals.