Canon 70-300 IS USM vs 70-300 L IS USM

Jules, thanks for the detailed info. I really do appreciate it.

One of the big things I will have to do at the camera store is try the lenses for weight alone. I've never tried a 1,000 gram lens so I don't know how it will feel.

I do know that my 15-85 at 575 grams is no problem.

The "L" and non "L" 70-300 are both about the same size and about 2" shorter than the 100-400L. So that's something in favor of both 70-300 lenses.

If 1000 grams doesn't feel too heavy then that would add points to the "L" and make the lighter (by 400 grams) less of an advantage.

My main reason for wanting a better lens is for wildlife on trips that I take. I've been going to National Parks for several years and wish I had discovered them earlier than at age 62. At 69 I'm not getting younger and not as steady as I used to be. So IS is mandatory. Especially since most hikes (some as long as 4-5 miles each way) are not condusive to carrying a tripod.

I'd probably like 400mm length but since my current 55-250 is close to my handling limit I should be realistic and go for 300mm.

A good, fast-focusing lens that's sharper than the 55-250 should allow me to do some cropping to make up for the lack of reach.

Also, 300mm as opposed to 250 will give me the equivalent of another 80mm cropped. That should also help.

Thanks for the good comments so far.