Out here, we get very high winds, I have bought every high-quality heavyweight flag and the heavier they are, the more they whip themselves to pieces.
The thinner, cheaper ones actually last longer, I get about one year out of the cheap ones.
That depends on the size you're looking at.
For a 3x5 home size, yes, sewn nylon flags are as durable as it gets. Annin and Valley Forge make them with sewn stripes and embroidered stars. They all sun fade within a year, but I haven't had any issues with either of these manufacturer's stitching or grommets before the flag was faded enough that I had to swap it out. They use multiple layers of stitches on both ends, and use solid brass grommets on the hoist.
I've found that cheaper flags (even nylon ones with sewn stripes) tend to have the stitching at the fly end unravel and get beaten up, but I can re-sew that pretty easily. Then the stitching at the canvas hoist end gets rust stained by the brass plated grommets.
Now for large flags (like what we fly on a 30' pole at work), we use polyester, but not the cheap printed stuff. Sewn stripes. The bigger ones have sewn stars too. They're very expensive, and very heavy, but they last out in serious weather where Nylon would be torn right apart when made that big. The down side, is that you need a serious pole if you want them to do more than just hang. They need to catch some real wind.
. Are polyester flags the most durable or high quality? House flag will be on a pole on the house outside and the shop flag hung in the shop from the ceiling ( checked with the code , seems proper )