After a bit of searching on the web, I might be able to answer my own question.
It seems the Pilot Sport 3 replaced the Exalto PE2 a few years ago
The Pilot Sport 4 replaced the Pilot Sport 3
https://www.tyrereviews.com/Tyre/Michelin/Pilot-Sport-3-PS3.htm
I can't work out why then they still sell Exalto PE2 if it has been replaced.
So looks like the Pilot Sport 4 for me, I would rather have the newer tyre design.