I am have a hard time Spending $2,700 for the Canon lens & $500 on the 1.4x??
Sigma tells me their 1.4x is better than Canon’s, I will have to rent one to find out.
Peter
Sigma makes good lenses. The less expensive ones will be softer at the longest end of the range. I would expect the more expensive ones to be better. I would expect the Canon lens to have better stabilization and faster AF, but how much better you want to pay for is a choice.