Clearos are great starting devices because they are easy to use, and now, with replaceable heads, easy to maintain. However, the best clearos don't give near the flavor and vapor as a good carto tank, imho. I tried over 40 different clearos in my seach for the best vape. I think the Protank II is the best clearo on the market, particularly when you build your own coils with cotton. Really good, imho.
However, a well primed, double punched Boge Carto in a nice Phiniac or IBTanked tank, is a far better vape, again, just my opinion. YMMV. But vaping is about all kinds of interests. For some, chasing the best vape is not nearly as important as saving money and not buying the newest shiny thing. For me it was the opposite, and while I appreciated the advice of the experts here on ECF, I still had to find out for myself what was best. What I found, is that different people like different things. Often, they just don't know any better. I remember when the vivi nova came out, everybody was raving about them. So, I bought several, different sizes, colors, etc. Was it good? Yes, but compared to what? Compared with a CE# clearo, it was great. Compared with a Protank II, it's not in the same ballpark. But, it's subjective, not gospel.
I've tried them all, pretty much, and your question is a very common one. It seems like there is a fairly predictable evolution in toppers starting with cigalikes => CE# top coils => RBA top coils (vivi nova) => RBA bottom Coils (Protank, Davide) => cartomizers => carto tanks => Atomizers (this can go anywhere and is often found earlier for juice tastings) => RDA's (Igo's, Origen) => RBA's (gennies-RSST, kayfun's (and clones), Ithaka's (and clones) => Advanced coil setups (changes to wick, wire, mesh, rope, ribbon, etc.).
Obviously, everyone's journey is a bit different, but there are better devices that CE clearos, though if they work for you, great. Also, building your own coils and mastering battery safety, Ohm's Law, coils, etc. is not on everyone's agenda, particularly new vapers. But, the longer you vape, the more curiosity you have, the more you read, etc., the more open you become to upgrades, variety, etc. The main thing is to enjoy the Journey. Your personal VapeQuest is yours alone, and what works for you, might not work for others. Personally, my ADV is a carto tank on a provari, but you can't beat my Kayfun 3.1 in hybrid mode on my Semovar. Best vape I've had so far, and best gear too. To each their own. Good luck to you.
A few different devices that I've tried and used. Some Displays. The Semovar/Kayfun Hybrid.
For me, I had to try them all, literally...