Selling my 70-200/F2.8 IS Mark II : alternative for indoor tele?

I'm not going to make a lens suggestion, but I have both the 100L and the 70-200L II IS 2.8 and my take on those two is this:

Image quality: both excellent, the 100L slightly better, particularly bokeh.

Focus: 70-200 is waaaaaay faster, even when the light is good (and using the limiters on the 100L).

Use: Most of my photos are on the trail. For that, I'll usually carry either a single lens, or three (50/1.4, 10-22, 100L macro). The 70-200 is often my single lens if I shoot with just one. Indoors I prefer the 100L over the 70-200 when there is good light because of its lighter weight. If the light is low or the subject is in motion, I prefer the 70-200 because of the faster focus.

I think you should try before you buy, because these issues appear small, but will be very important to you.