Keep both. I use both extensively. On trips that require a size/weight mindset, I bring the small one. For everything else I use the bigger one - one of my absolute favorite lenses. Not the best choice for hikes or when you don't want to be too conspicuous but otherwise a true winner.
Edit: please ignore all of the below, I somehow misread the question and thought it was about the 24-105 f/4L.
But, on the subject of the 24-105 f/2.8 Z, I own this lens and actually think it is an exception to my "compromise" statement below. Not only does it offer a fantastic focal length range, but superb rendering and contrast. The images I have captured with this lens almost jump off the screen.
The only downside is its size and weight. Which is of course what several other commenters have mentioned.
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Well, you could replace both of them with a 24-105 f/2.8 IS Z. Or, alternatively, with a 28-70 f/2.8 IS STM (for the other extreme), haha.
Kidding aside, I think for general travel, landscape, scenics, etc., an f/4.0 zoom is ideal, and it gives you the more useful range without having to also carry a longer lens.
For when you need something faster, you could always pack a 50mm f/1.8 or 35mm f/1.8 prime. Both are small and light enough to carry mostly anywhere. The primes will always deliver a more "prime like" look than an f/2.8 zoom, if that is what you are after.
F/2.8 standard zooms have their place for photojournalism or event work, but they are a compromise, really.
Use them both and see which way you gravitate. Though with the 24-105 being a gift from your very kind and loving wife, it's certainly the wrong one to sell for non-photographic reasons.
IMO it kind of depends on what other lenses you have in the system. If you have a 70-200 then the 24-105 kind of overlaps it while being similar in size to a 70-200/2.8. It might pair better with a 100-400 or 100-500. Alternatively, given that the 24-70/2.8 isn't exactly a tiny lens in its own right, there would be some benefit downsizing it to the 28-70/2.8, which would pair nicely with the compact RF 70-200/4 or RF 100-400 and the 16-28/2.8 on the wide end.
I had a quick browse of your pbase collection and it seems like your most recent uploads were mostly shot with the 90D. What are you using from the R system and what are you mostly photographing with it? Travel type photography?
Perhaps I am stating the obvious, but I think the first thing to do is get your wife something she would really like as a way of thanking her for this very nice birthday gift. After that as you build your kit, as always it depends on what you shoot and what resources you are willing to put into photography, but In this case selling the 24-70 and putting those resources into something else makes a lot of sense. Do you want to be able to shoot wider? Do you want to be able to shoot longer? Do you want other zooms or do you want a prime or several primes? There are lots of good options, but the 24-105 f/2.8 is a great place from which to build a high level kit if the weight doesn't bother you too much.
For wider zooms the 10-20 f/4L, the 14-35 f/4L, the 15-35 f/2.8L, and the 16-28 f/2.8 could all make sense depending on priorities for coverage of wide angle, size and weight, and expense.
For longer zooms the 100-300 f/2.8L, the 70-200 f/2.8L Z, the 70-200 f/2.8L, the 100-500 f/4.5-7.1, the 70-200 f/4L, and even the 200-800 f/6.3-8 could all make sense depending on priorities for coverage of focal length, size and weight, and expense.
There are so many primes to consider I won't even both listing them, but the VCM L primes, the f/1.2L primes, and even the IS STM Macro primes and the 100L Macro primes are worth considering and then there are the long primes to consider as well. Any of these or perhaps several of them could make sense to add to your kit depending on your priorities and your budget.
