Timmy G was referring to what John told me, which was that the 'Series 2 has a better turbo'. He didn't mention anything technical, he just said 'they are slightly more powerful and smoother than the Series 1'.
Unfortunately, that's all I had to go on, not sure whether it is indeed better or not as I have no idea about the technicalities. Could've even been to make a sale for all I know but I basically just trusted John on what he was saying.
As for the ceramic impeller stuff, I agree that ceramic would logically be better than plastic. So in the end, I'm back where I started, no idea as to whether a Series 2 turbo is better
But as JimX said, I guess it doesn't really matter at standard boost anyhow, so all is good.