Have you talked to your insurance agent about it? I ask because I am a former agent and we usually would have required at least the option to repair or proof of the actual replacement cost with a new item. Things do get a bit more interesting with something like this that is no longer available new (at least I don't think it is).Don't automatically assume that you will get whatever it is insured for, that policies I worked with wouldn't have done that. In other words, if you have not yet spoken with your agent, do so.

Back to your actual question. I think you would be better off with a very nice used one if you are getting enough extra to cover a CLA on it. You can assume that it likely has not suffered the kind of trauma that your lens has and that all it will likely need is a CLA. Given that choice, I would probably get the used one.