Canon EF 70-200mm f/2.8L IS II - or - Canon EF 100-400mm f/4.5-5.6L IS II

The two lenses you mention are very similar in size, weight, price and sharpness (excellent). The question is, would you rather have one more stop of aperture than your 70-200 f4 or a lot more reach?

Since you mention your typical use is people/family/vacation and that you would need the extra reach only occasionally, the 70-200 2.8 II seems like the better choice. Your 70-200 f4 should also work pretty well for that though, with a much more travel-friendly weight.  May I ask you what made you think of upgrading in the first place?

Pietro Marchesi wrote:

I plan to upgrade my excellent Canon EF 70-200mm f/4L IS to the even better Canon EF 70-200mm f/2.8L IS II. Then enter the Canon EF 100-400mm f/4.5-5.6L IS II.

I use a Canon 6D and sometimes my old 20D as a second camera for reach 112-320mm.

My lenses in order of use: 24-70f/2.8L II IS, 70-200/4L IS, 16-35f/4 IS

My photography is mainly of my family, street life, people, architecture, travel and vacations, 5-13y old kids, in/out doors sports and some wildlife.

Some times I really miss my Canon EF 400mm f/5.6L a very good lens but it really was not very convenient to use for my needs, it caused lots of lens changing, I wish it had IS and a lot shorter minimum focus distance than 11.5' / 3.5m. More reach than 200mm would be great but only occasionally.

Q1 - Browsing the net it is hard to find many user examples of family/kids/people taken at the 100mm short end of the 100-400mm f/4.5-5.6L IS II is this lens made mostly for 200-400mm birding and wildlife?

Q2 - Please post some of your photographs of family/kids/people taken at the 100mm short end of the 100-400mm f/4.5-5.6L IS II.

Q3 - How well can the Canon EF 100-400mm f/4.5-5.6L IS II replace the Canon EF 70-200mm f/2.8L IS II for mainly people/family/vacation use?

Hard choice, clearly two very good lenses.