As I was recently told due to experiencing fluctuations again with plastic sets..."if you are small (size 10/12 or under) and lean and no fat then plastic sets can kink and flex and block so they aren't recommended."
I am pretty much proof of this as almost 5 years ago I knew there was a problem with one type of plastic set. They did get withdrawn. This time round of using another plastic set because metal ones weren't available there has been wider fluctuations in levels consistently for time on the plastic ones. Have jyst gone to the new metal ones 2 days ago and back to stable bloods again.
I think size, activity and where you wear them has a lot to do with set choice. A bit like suck it and see.. As I know there will be size 10/12 people that get on fantastic with plastic sets... All choices have to be personal to you as the individual.
Its not just based on plastic or steel though. Its also down to length of the cannula. I'm 6mm steel. 8mm are again not good for me as I am lean, no fat. Consultant suggested 4mm but My manufacturer doesn't make them. Again there will be size 10/12's that will be using longer lengths...