Its super easy to build and setup, and the adjustable airflow is great for beginners so they can have the option to try an airer/tighter draw without having to permanently damage the atomizer. It also gives the option for dual/single/U-wicking as well as an open chamber vs closed off chamber. Basically, you can run all sorts of setups to figure out what you like before getting something else.
Yeah, you can use it with cotton, its actually designed to accommodate it, but if you are going to use cotton, no sense even get into a genisis tank, you will be far better off with a Kayfun/Taifun/Squape/ etc...
Personally, for me, I don't like adjustable airflow/chamber, I'm fine with a permanently fixed airflow with a micro chamber since I'm pretty set on what I like now:
If the Sat was too tight, then you wont like the RocketR in its stock configuration, even less the MCR or Hellfire atties. Fortunately, you can have the Rocket cap (and MCR) bored out to your preference.
Flavor wise, both the MCR and Rocket-R are my top 2 picks of all the genisis tanks I've used or tried so far. Overall though, I wouldn't trade the Rocket-R for anything out there, its the first genisis, or any atomizer for that matter that actually checked off all the boxes for me.
Close second is the Squape R (s) since it works great with mesh
For me, its my leak-proof genisis that I take with me for travels. The only downside is the chamber is really setup for cotton builds so flavor isn't as intense as a proper genisis. Still, its close enough