I'm considering upgrading to get better high ISO performance.
It's great having f/2.8 lenses but the weight when flying is a problem, as is the bulk.
No way would I put a 300mm f/2.8 in the hold baggage, or the 24-70 or 70-200.
That means hand luggage is nothing but kit

Going to smaller, lighter, slower lenses means I need bodies that will give me better high ISO performance as I make the 2 stops difference up with higher ISO - and I get some of my carry-on space back

So I would be trading size & weight for lighter carry-on kit, and ISO for f/ stops.
I suppose the difference is I know what I'm doing, and why.
And if I was starting out today, if I had no need for the smaller DoF of the wider faster lenses, then I could also save a lot of money on the lenses, too.

I'd also get more use out of my 100-400L which is lightweight but needs to be stopped down to about f/8 to get the image quality I expect from an L lens (reduces vignetting).