I had both in hands, and for me those almost 2 cm is a big size advantage for me with the R50.
Esp. when you take the size of the lenses (WA to TELE) into account.
I also considered the R8. It is not much smaller than my R6m2. But the R50 is much smaller.
But more important is, when you pair the R8 with a 24-105 STM or the 24-70+adapter: the combo is noticeably bigger than the R50+Sigma.
Give me the R8 specs. in an R50 housing, and still I would tend to the R50, because of the Sigma 18-50/2.8.
It is not 100mm FF eq. at the tele end, but close (80 mm FF eq. - for those that don't want to calculate), AND it's f/2.8 (at APS-C).
It was a long and hard decision.
But I made my choice.
And I wanted to stay flexible with an ILC system instead of P&S.
Choice is good! I do see the potential benefit of APS-C for a travel ILC kit, but for me the R50 doesn’t get there. The M6II does, particularly with the lenses factored in.
Here’s how I visualize it:
The three cases are sitting in my carryon suitcase (Pelican Elite Luggage Carry-On, long discontinued, but as I pointed out
here, I’ll never need to buy another one).
In front is a Think Tank Retrospective 5 v2, for my FF travel kit. That currently comprises the R8, RF 10-20/4L, RF 24-240, and one other lens of similar size (last trip it was the RF 24/1.4L). The RF 28/2.8 and a little flash like the 270EX II will also fit.
Above left is a Think Tank Mirrorless Mover 20, for my M travel kit. That comprises the M6II or full spectrum-converted M6, the M11-22, M18-150, M22/2 and 270EX II (along with IR filters as needed). Realistically, I suppose the R50, RF-S 10-18, and RF-S 18-150 would fit. Not sure I’d be able to squeeze in the Sigma 32/1.4, and I’d need the adapter to use a small flash. Plus…I already have the M kit.
Above right is the LowePro DashPoint 20, which will fit the PowerShot V1.
Like I said, choice is good and the right answer is what works for you.