[gnuuser]

6011 rods work well ac or dc but dc reverse polarity will give deeper penetration in your weld
6012 will be harder to strike an arc on but can produce some damn fine welds in skilled hands.
we use a variety of different rods at work including 6010, 6011,6012, 6013, 7014,7018, supercast, a120 (chrome rod),super-blue and super gold (the last two i dont use much and dont care for)
they are easy to weld with but in many cases unsuitable for many welds being too brittle
super-cast is good but smells like burning cow s#1t when you use it.

try to choose a rod that is closest to the chemical make-up of the pieces you are welding
most of the rod guides can be a big help there

[Edgewalker]

Me personally.I love 6010. I wouldn't get anything "low-hydrogen" without an oven. It does not make sense to buy a 7018. You pay for a low-hydrogen rod to limit the input of hydrogen into the weld pool. Then do not store them in an oven which introduces hydrogen into the rod and thus the weld pool. Will an old and exposed 7018 work? Probably, but what about the time that it doesn't?