SX3 or SX3 S1

[carnage]

Hi all,
I'm returning to the UK after 10 years in Australia, I raced off road for 4 years then raced on road for the last couple years, as on road suits my skill level as I've got early onset parkinson and off road was too re-active,
anyway I'm looking forward to racing (ATM at DMS) and looking at getting an SX3,
My question is about the difference between the CF sx3 and S1 version, I've heard the S1 is easier to drive , prob due to more flex??? is this correct,
I'm looking to have compettitive fun,
cheers
Steve