Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
I have 1/2" and, while it does make it easier on the hands, the weight of the sheets is a factor in light winds. I'm thinking about changing to a thinner line.
I use 7/16 because it works better in my Lewmar 16ST's. 3/8 kept coming out of the grip at the top. I also use single braid -- the soft stuff without a core -- because it's so nice in the hands.
Oversized lines are a problem for the reasons others have said. If you want to reduce the effects on the hands, there are lots of balternatives that are better than using oversized lines. You can put an extra wrap or two on the winch in stronger winds, you can wear gloves, you can use the winch handle in stronger winds. Don't try to do it all with your bare hands. Use the mechanical advantage that the winches offer.
I use 3/8" on my 110 jib and 1/4" with my 150 genoa. When the wind gets light I switch from 3/8" to 1/4" on the mainsheet also. Halyards are 1/4". I've found the problem with bigger lines is the drag through the blocks especially with every thing led aft to the cockpit. I'm switching to 3/16" on all my lighter load lines like reefing, main downhaul, lazy jack, etc. I do wear gloves and use all four winches.
I use two or more wraps on the winch, and winch handles. I don't have light air problems -- I fire up the outboard (I do not race). There's plenty of room left in my genoa blocks.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.