You also vape differently then many in this thread, for me Neither the Engine, or the Engine Nano come close to either of the Merlins. Actually the Engines are fairly far down my list for flavor, I can think of 10 atties off the top of my mind which beat them. For me the only thing they really have going for them is dead easy to build/wick and nearly leak proof.
Press fit positive post is a huge negative on them, for that reason alone I wouldn't recommend. As more of them make it into the wild, I'm seeing more & more having issues with the post popping out and/or loosening up. Very sad that OBS did not learn from the Crius Debacle.
Edit: I'll also add that if I recall correctly you only vape a very small variety of juice, was it one or two tobaccos last I saw you mention? Its entirely possible it does very well with some flavors, not so well with others. Certainly wouldn't be the first time I've seen it.