I own a mixture of Canon and Sigma. I love each one for different reasons. For example I would not trade my 35L for a Sigma 35, the same as I would not trade my Sigma 85 for an 85L. Once we become used to what a lens delivers, know how to use it and we like what it delivers it becomes harder to switch. An example of this was my Canon 50 f/1.4. Even though I was used to it, I was never impressed with what it delivered, so made the switch to Sigma. I had a bad copy first up, but the second one is OK. If it had also been a dud I would have probably gone with a 50L, but it is a good copy and I like the depth of image it delivers, so I’ll keep it. If people have issues with what their 35L delivers I can see why they would want to swap. I have no issue with mine, in fact I love using it, so really am not interested in comparisons between the 2. I think many others are probably the same.