Number one is the Reload Vapor USA ~ OG Reload (24mm RTA). Short answer, it's because it is imposssible to know why unless you've tried it. Long answer, all the other RTAs excepting only the Deathwish Modz ~ Isolation (26mm RTA) are incapable of holding a candle flavor wise to the best flavor RDAs. Both of them are extremely hard to find now. You'd almost certainly have to buy used. Even then, the used ones either will be completely battered to the point of having been reduced to scrap metal a few years ago or will still be very hard to find. Or worse, people who have them never sell them─due to how great the RTAs perform.
They are relatively expensive RTAs, which makes them overpriced especially according to those who have never been able to afford getting them. The reason why positive user reviews are scarce is due to a combination of factors. Firstly, if more people are convinced that the RTAs are overpriced, then fewer people buy them, no matter how much these people can afford. You have to WANT to afford these things. So, it's a hard sell. Reviewers on YouTube don't make enough money from subscribers and likes, if not enough people are interested in the product under review. Whatever it is that YouTube claims to be better for flavor, that's what most people spend their money on. So, it's all about marketing. I.e., not about the flavor. Getting people to try properly installed (and properly wicked up........), handbuilt, complex, coils of various types to get a rudimentary shred of an idea of how flavor can be like is even much harder than it is to fight against windmills. Next thing you know, YouTube starts to remove content and starts shadow banning people's account. And you already know why.
In a nutshell? If people are too lazy to learn to buy a proper set of handbuilt complex coils and get the coils ready for vaping, let alone learn to BUILD a poper set of complex coils with just a cordless drill and a swivel tool, then is it really any wonder that they don't understand about flavor? Personally, I, own a multi-thousand Euros collection of RDAs, the vast majority of which are high end. That doesn't make me an exception, though. My determination and my dedication to my flavor chasing hobby do. Whereas those who always were more interested in showing off their coilbuilding skills purely for the sake of using the pics to achieve marketing goals have left the building (and have left coilbuilding). There now, I said it........