Pros for sub ohm tanks: No fuss, stick a coil in, prime, fill, vape. Cons: Coils are pre-built, you have no control bar buying different resistances they offer. Coils don't last very long, and they're not cheap.
Pros for RTA: Most of them are easy to build on, you save money over time, flavour is generally much better than pre-built sub ohm tanks/coils. Cons: Well, you have to build your coils, buy wire and cotton and some small tools to set up at first.
I haven't used a pre-made coil since I began building my own coils for RTA, even my Cleito now has the RBA deck. It's easy to do once you get the hang of it. Once you can build one, you can pretty much build them all. I like having control over the resistance, the type of wire, the type of cotton, the flavour is great, it'll always be better than sub ohm tanks. Watch some videos on making simple coils for RTAs and see just how simple it can be.