Being that the OP said that he/she is getting tired of using a vape with a limited bowl space and that the vaping will be done mostly through a bong, I gotta recommend the LSV.
But if it had to be between the EQ and the DBV, I would opt for the DBV, unless the vape is going to be used for party situations more than just occasionally, because nothing beats a bag for those situations. I also don't like the air path that the EQ requires and being that the DBV has no moving parts or electronic circuitry, there is less to go wrong on the reliability front.
I agree with the basic facts that you present, such as the air path concerns. But I have seen plenty of DBV's stop working, in some cases it just wouldn't turn on anymore, and other cases the shitty and very cheaply applied JB-Weld that is used to fix the base that the heater seats on would just give in, leaving one with a very loose and wobbly heater that is both unsafe and just not acceptable.
That JB-Weld issue has happened to one of my DBV's as well as two of my friends. And with production in China I would imagine QC is even worse now. Of course 7th floor has great customer service(as does Arizer IMO) and gladly fixed all these issues for free, the only cost is the user's time. My extreme has never failed yet, even though it should have way more potential too.
Also, since I mentioned the fact that the DBV is now produced in China, I feel it is important to say that the Extreme is still made in Canada, as far as my knowledge, so please correct me if wrong. Neither are American made unfortunately, but I'll support and trust Canadian labor and inspection much more than Chinese.
Also, it's nearly impossible to combust in the Extreme, however many times I have seen a DBV become an accidental combustion device. I just won't own a vape that combust so easily, that's exactly what I am trying to avoid in the first place.
Both great vapes, this is just more evidence that you need to research and decide what you need and like in a vape.
Now I know why these threads are pointless ahaha