I can comment on some of the QaromaShop stuff; I have both the Qaroma and the Taroma 2.0. Contrary to what some have said about ball vapes all being more or less the same, I've found that this is not the case.
Both the head design and housing material affect draw, flavor and effective extraction temperature.
Whether the difference is appreciable to one ent vs. another is purely personal taste. My Qaroma (fused quartz) has very different flavor than the titanium Taroma, at the cost of a significantly higher operating temperature.
In my opinion, though these units cost more than a DIY option, these are a buy-it-for-life item and worth the one time added expense.