How important is the size of the jig? I’ve heard smaller is better and the exact opposite - bigger is better.

I’m going to have to go with my personal preference on this one because you’re right.  Depending on who you’re talking to - you’re going to hear it both ways.  The wonderful thing about the jig is that it is one of the most versatile lures on the market.  Jigs today range in size from 1/32 of an ounce to ½ of an ounce.  It does seem to me that fishermen today tend to use the smaller jigs but I’m not real sure why.  I prefer heavier jigs and with good reason.  The most important thing a jig does for me is it allows me to feel the bottom - when I use really light jigs, in my experience, it’s more difficult to keep them there and it seems that I lose contact with the bottom more than with a heavier jig.  When fishing rivers, like the Missouri, the depths change quickly, the jigs I found that worked best were either the ¼ oz or 5/8 oz.  I’ve caught more fish using these sizes than any other.  I also didn’t experience near as many bite-offs as with the smaller jigs.  Give it a try next time you’re out.  In my opinion, bigger works better.