My CRS is 417 too. I scored in IELTS LRWS 8 9 6.5 7.5... I am short 0.5 point in writing to score CLP 9... Though, I am not sure I can get it if I take IELTS again. And since I cant wait, I submitted my Ontario application yesterday
So, if you are confident you can achieve 8 7 7 7 if you take the IELTS again, then go for it.. This is your best option... Otherwise, accept Ontario invitation... I am against the waiting option... No one knows what would happen to the rules and regulations of IRCC tomorrow... and no one knows for sure when the quota will be filled (quota for ITA or for Ontario nominations).
All the best.