It's all about what you like, and don't like, about your current set-up.
For me, started with cigalikes. Made 'em work for months, then went back to smoking. Restarted with an ego and things were significantly better. I knew that by last summer, egos were old technology. So I wondered: if the jump from cigalike to ego was such an improvement, what would happen with a better atomizer and an actual mod? So I got a 15W mod and started rebuilding. Wanted to experience more power and more vapor, so I upgraded again, landing on the 45W builds I'm using now. All of these transitions were held for at least a month before advancing further.
So, the question is: do you want more vapor or the freedom to build coils to your liking?
If yes, my advice: "sub-ohm" is really a badly-phrased way to say "high power". Anything higher than 15W would need sub-ohm builds on a mech. Thankfully, you don't need a mech for high power! I'd grab an iStick 30W to test the waters for like $35. Of course you'll need an atomizer capable of higher wattage. I'd learn to rebuild with a dripper like a Magma, personally, but I know a lot of people like the "sub ohm" marketed tanks like Atlantis, Melo, or Kanger's sub ohm tank. I prefer rebuilding, because you can build exactly what you want. My 45W builds give of a lot of nice, cool vapor; I can't stand a hot vape.
If you're happy where you are, don't worry about. But if you're curious/wanting, all I can say is that high-wattage and rebuildable dripping atomizers are my happy place
