But if you want big monster clouds that make your head disappear it wont happen with any tank.
^^^This.
As of right now tank's can't compete with RDA's (for cloud chasing) IMO. For an RDA I have an El Cabron and for RTA's I have Subtank Mini and a Lemo Drop. The El Cabron blows the other 2 out of the water on both vapor production and flavor. Period. End of story. It's not even a contest.
Now with RDA's out of the picture lets talk RTA's. Both that I have produce great vapor and flavor. Which one do I like more? Well, strictly considering vapor production and flavor the Lemo Drop wins hands down. Though I did have to modify the air holes to get better air flow... Stock, the Subtank Mini has better air flow... Out of the box the Subtank Mini is a better RTA IMO. It has better air flow options, easier to refill, you can rebuild when you sill have lots of juice in the tank unlike the Lemo Drop (PITA to refill). The RBA section of the ST Mini is bad ... but if you aren't into rebuilding then you have the option of purchasing the OCC heads which just screw in and your ready to vape. So the ST Mini is much more versatile and can be used as a 'clearomizer' or RTA.
From the title of your post it sounds like you aren't into rebuilding, if that's the case then it's a no brainer. ST Mini (Or some other sub ohm tank that has replaceable coil heads, like the Aspire Atlantis [I've not used it]).
To Summarize - If someone wanted to have a cloud chucking comparison of RTA's, I'd bring 'MY' Lemo Drop, no question... But if someone wanted to get into cloud chasing (and not interested in RDA's) in the most simple way possible with a well designed system that is easy to use, I'd say go ST Mini. It really is a well thought out device and I have zero complaint's about mine, other than I don't like the OCC heads. But I rebuild them to what I do like, so, no complaints.
I haven't tried any other type of RTA's, so it's only based on what I've used.
Good Luck,
-Lost