You are using a T6s that can use EF-S lenses?

Personally I wouldn't get any of the Canon 24-105s (there is also a non-L, STM version) to use on it. They just aren't all that great. The primary difference between the two L's is that the newer one has improved image stabilization and uses Canon's new Nano USM auto focus drive.

For use on an APS-C camera like the T6s, either the EF-S 15-85mm IS USM or the EF-S 17-55mm f/2.8 IS USM would be a better choice, in my opinion. Better image quality, better range of focal lengths for an APS-C camera (on the one hand) or a larger aperture (on the other hand), just as fast focus and just as good IS. Probably just as durable, too. (The new 24-105L still has to prove itself over time... the original wasn't all that durable).

If you were using full frame, I'd recommend the EF 24-70mm f/4L IS USM instead. That has almost the best edge to edge image quality, just slightly short of the 24-70mm f/2.8L II (which cost twice as much). It's also the closest focusing, with a "Macro" mode that actually manages 0.70X magnification (about double what the next closest non-macro Canon lens can do, triple or more magnification than possible with many). But I wouldn't buy that lens just to use it on an APS-C camera.

Folks think they "gotta buy an L" for top quality... but that's just not true. While most L are excellent, some non-L are just as good. Particularly among the EF-S there are a few that perform as well as any L... and in some cases even better than some Ls.

There isn't now and never will be an EF-S lens that's an L... But that's only because of how Canon defines the L-series. Among other things, to qualify "an L must be compatible with all EOS cameras, past, present and future". And EF-S lenses aren't. They can only be used on the APS-C cameras.

But even without a red stripe and an L in their name, several of the EF-S lenses manage to perform just as well or sometimes even better than L. The 15-85mm and 17-55mm are two... A couple more are the EF-S 10-22mm USM and the EF-S 60mm f/2.8 Macro USM.

EDIT: Yes, I'm aware that the T6s can use both EF and EF-S lenses. That's one of the nice things about crop sensor cameras. With croppers there are more lenses to choose among. With full frame cameras you are limited to only full frame capable lenses.

I am looking to purchase another "L" lens refurbished through Canon. They have the 24-105 II version on sale for $779 (as of today) and version I not on sale for $799. I have been watching videos. They say there isn't that big of a difference between the two lenses. The II version is heavier, but has quieter image stabilization. Otherwise the optics are basically the same. I know the I version is older. Does anybody have any comments with either lens? I love my 100-400 L II refurbished lens on my crop T6s. I'm certain the 24-105 lens would serve me well. Thanks in advance.