I have been looking for a Sony FF lens with a lot of reach for a while. Difficult decision between the 100-400 and this 200-600, but the price difference sold me ($3.4k for the 100-400). The 200-600 is usually about the $3k mark (some places you can get close to this deal price, but I can't find it cheaper). Yes, the 100-400 is WAY more compact, and possibly a better lens across the board (especially for traveling), but at the long end, it looks like the 200-600 beats it once you crop in to make the subject the same size, and lets face it, that is usually what we use these big lenses for.
Spanning a versatile telephoto range, the FE 200-600mm f/5.6-6.3 G OSS from Sony is a flexible zoom perfectly suited for nature, wildlife, and sports applications. Its long reach pairs with a modest maximum aperture range to render to a relatively lightweight and portable design, which benefits handheld use. The optical design incorporates a series of low dispersion and aspherical elements, which suppress a variety of aberrations, color fringing, and distortion in order to produce well-corrected imagery with high sharpness, color fidelity, and accurate rendering. A Nano AR Coating has also been applied to further reduce surface reflections and flare for improved contrast when working in bright and backlit conditions.
Dang. Bought one with the Amex cash back for $2,915 a couple of weeks ago. Still a good price but the Digidirect is pretty good. I think the lens was around $2,600 in January.