Flag occupation definitely conveys more information than colored stripes in a game where you can have numerous countries of quite similar map coloration. I would also say that in my subjective opinion the flag occupation looks a lot better in-game than it does on a screenshot. Stripe occupation is not particularly visually pleasing, it's just that it's been the norm in our games for a long time and gets a pass for this reason.
With all that said, I think we could still do more to iterate on the flag occupation and experiment with different scaling, tiling and transparency, but I still consider it an improvement over stripes regardless.
It still presents a problem at associating with what we see on the map.
Besides what
@FranklyJustNess said you'd also need to have a deeper knowledge of flags to get the information presented there, which can be quite dynamic.
With colors, however, it's directly present on the map, even if you have no idea who's which flag, you can see the color on the map right there, so it's much easier to read.
Like, for example, what happens when we get something niche like a communist Tibet, with a completely unrecognized flag?
If the occupation is done with flags, you'll have no idea what's going on until you click around and find the flag for yourself.
If, on another hand, it's done by stripes, you can tell just at a glance "ah, the green country is invading the yellow country", I hope you can see just how more intuitive that is.
A nice exercise in this would be playing the
flagle.io game daily, see how many flags you can recognize.
The way I see, Vic3 is essentially importing this guessing game.