I have no personal experience with 'Epic Plastics Epic Edge' so not going there. I fixed other peoples edging and it looked like Benda Board but never found out brand name, but it was flexible. I didn't have to replace it. What i had to do was straighten it up since it started to angle....in these photos, notice that grading is added to both sides so angling shall not occur https://www.google.com/search?q=benda+board&client=firefox-a&hs=lwu&rls=org.mozilla:en-US:official&channel=fflb&tbm=isch&tbo=u&source=univ&sa=X&ei=ak8eVLPyE4u2yATo9oG4AQ&ved=0CCwQsAQ&biw=1366&bih=605

But i'm not a fan of plastic/steel edging unless you got plant ground cover to mask it. Use rock, especially if the 2 grade levels differ in elevation http://www.bobvila.com/wine-bottle-edging/44302-on-the-edge-16-garden-borders-you-can-make/slideshows#.VB5VSRauSSo

I like to use 18 gauge sheet metal. I have a fabrication shop cut them to size runs $11 - $13 for a 10 foot length. Doesn't have a rolled edge like most out there, this allows sharp curves without kinking.