The first things that I would consider are:
1)Size & Shape- Do you want a PV that is the approx size & shape of a traditional analog or are you looking to explore a bigger and less
2)Battery Life: How often and how much do you vape? All day away from home? Are you looking for a PV that has longer battery life than the RN4081 or has that been OK for you? Have you thought about trying a higher voltage? Maybe 5 volts?
3)Cartos or attys? Sounds like you prefer the cartomizer. That should help you rule out the others.
What is the main reason you want to get a different PV? Are there some things that you want to improve on in comparison to the RN4081?
I know I'm answering your question with questions, but IMHO, that's what you need to do. Ask your self these questions.
Maybe make a list. Things you like and dislike about the PV you currently have. Most folks that enjoy the
vaping experience usually end up buying 3 or 4 models before really settling in on one in particular.
You might want to read what other members say about specific models here:
Model Specific Discussion
Good luck in your search for the next PV!