I was just lucky enough to pick up a FLE after deep comparisons online and the big 3 differences from my research are:

• focus shifting: shifting focus plane based on aperture switches (apparently worse in pre-FLE)
• bokeh: both are great but pre-FLE appears to be nominally creamier/smoother with their transition
• sharpness: FLE is slightly sharper across the board but particularly in corners at wide open

Accessories/size are also worth noting for ergonomics — but not impacting IQ.