Yeah, i also don't see much of a difference. Both are very readable to me but as you said a lot of people say that the scroll format is better. So that was the main reason for the question.
And theres also the thing with Tapas and Line pushing the scrolly format. If you want it to reach a wider audience, you would naturally have to follow what the platform wants ;-; but i dont think i have to stress about that at all because the first one is never that good lol
And i dont necessarily agree with you on the fast read part. The scrolly format has a few good things to it. Like compostions you cant pull off with manga. I have read a quite a few great webcomics like I Love Yoo or H&H Roman Company. And imo Line and Tapas want the scrolly thing to be a thing. Manga is the japanese format. So i am guessing they want something different to that. I dont think the format should be devalued just because its different. Every format has its pros and cons and its up to the artist to compose it in a way that the story gets through to the reader.