One nice feature of PEX is that you can get it in colors besides grey, green, or white. Red might be especially useful for Xmas displays, blue might be relegated to a 4th of July display.
I use two 10'x3/4" grey electrical conduit for an arch over my driveway, don't have any problems getting it into the shape I want. One end is secured to a 4x4 post ~6' off the ground using PVC pipe clamps, the other end slides over a piece of rebar which sticks up about 2' above the ground. It does sway in our winds, but it has survived 4 seasons so far without losing shape or falling over.