Originally Posted by Ade
Both are excellent lenses. I had the 200mm f/2.8L II for a while, sold it in favor of the 70-200mm f/2.8L IS II - but that was for those 'other' reasons, namely versatility, IS, and weather-sealing. From an IQ standpoint in real-world use, the 200/2.8 was excellent.
Originally Posted by Ade
They don't get 'stealth updates' from an optical standpoint, but there are 'stealth' repairs (sometimes not really stealthy) - e.g. the 24-105mm f/4L initially had a specific issue with flare, which was corrected in later copies (in that case, Canon issued a service notice and fixed the older copies). I suspect there are sometimes stelath updates from a mechanical standpoint, though.