They taste absolutely the same to me in either tank. BDC or BVC, I wouldn't go out of my way to get one or the other as they both put out the same flavor and cloud no matter whether I'm on a Naut mini or the 5ml tank.
So, here's my theory on this... Using the same battery, same eliquid and the same coil, that leaves the only difference being a larger tank. In my mind there is no possible way that the larger tank is going to produce less or greater flavor since to me it really all depends on the battery supplying correct power, and the coil that is ingesting the liquid into it's core and the type of eliquid. To me (and I've got both tanks, and tried both coils on each with the same battery and eliquid) there was no difference.
With that said, buy which ever one you are more comfortable with. I use the 5ml size with the stainless steel caged tank instead of the stock tank for a little extra breakage protection and in general use the 5ml so that I don't have to carry around any extra liquid bottles when I'm out longer than normal.
Enjoy, both work great for me.