To me, who never want to age my beer long term in a fermenter, the main difference is plastic can get tiny scratches easily which allow bad crap to grow and cause issues with infections. But I have never used a glass carboy due to the price. Anytime I think any one of my fermenters look scanky / scratched internally I just chuck it and get a new one. Under $20 for the Bunnings fermenter, it is wort less than the wort we are putting into it.
Side note, anyone see Bunnings now have square 30L drums with the large round opening, they are only just a bit taller, and still under $20. When ever I need to replace mine these are the new puppies.
QldKev