But resource consumption leads to battery consumption. And since there isn’t any difference in physical size between a midrange and highend hardware, the only thing that can change the physical size of the phone, while keeping the same performance, is the battery. (And maybe the thermal design)
I don’t have any experience of those brands specifically but I have had a couple of similar phones.
Performance wise I don’t think they are quite up to speed with the SD835. But as @pauliunas said earlier, midrange hardware is plenty for almost everyone today.
But there’s two things that are big negatives for me, customer service and software updates/hackability. The customer service is often sub par with these very cheap phones.
But the biggest thing, for me, is that it is much less likely to be updates to future Android versions. And these phones don’t get the attention from the modding community and therefore there’s little chance to be able to “update” your phone yourself.