HELP ME CHOOSE!!....which should I take?

Why does your friend have so many lenses with such a similar range?

Bring a camera to his house, take shots with all four, and pick the one that takes the best pictures, thats my vote.

A couple are his, and some are his father...(he passed away, so he's got his stuff as well.)

I tried the lens, and I seem to like the Canon 100-300 and the Tamron 70-300. To me, the Tamron looks a bit sharper, after about the 200mm, but they both look similar from the 100-200 range. The motor on the Tamron seems a bit loud, but it looks almost brand new. He only used it for a few months, and then both the 70-200L lens...

The sigma is nice as well, but from reading previous posts, people seem to prefer the APO DG version over just the DG version.

Oh, I guess I should mention....aside from candid people shots, I also wanted to shoot the moon, airplanes etc.. Not so much for sports.

the ef 100-300mm