In case you are wondering how to tell a cheap cord from a good one, look for the wire size.
Wire gauge gives you a comparable specification and a minimum size you have to meet or exceed, but it doesn't really say anything about quality within a given gauge. It's not hard at all to find a cheap, poorly constructed 14 gauge extension cord, and I'm sure I could walk into a Walmart and find a crappy 12 gauge cord as well. The plug ends are very important once you select 14 gauge or larger: if the contacts are inadequate or the plug or socket is poorly molded, that's a bigger danger than using a high quality cord with a marginal gauge.
They also say to avoid lighted cords. I've never had any trouble with those. but I may just have gotten lucky with the one I use for our outdoor EVSE...
Oh, and remember, newbies, that as the gauge number goes up, the wire gets thinner
, not thicker! 12 gauge is heavier than 14.