I switched from the Clever to the Bonavita under the assumption that porcelain would hold heat better than plastic. I never bothered testing. Then I saw this video by Scott Rao wherein he recommends the plastic V60 over the ceramic and metal ones.http://www.youtube.com/watch?v=c0Qe_ASxfNM
He claims that the plastic V60 holds heat best and recommends proving it to yourself by touching the sides. So I tried that with the Clever and the Bonavita. To my surprise the Bonavita was a lot hotter to the touch, implying it was seeping heat out more quickly than the Clever.
I did a test with a cooking thermometer. I performed the following with each brewer. From a variable temperature kettle I used 200° water to preheat the brewer. I emptied the brewer and then filled it again with 200° water. I immediately inserted the thermometer. I noted the temperature at 1, 2, 3, and 4 minutes. Here are my results.
1 minute - 190°
2 minutes - 183°
3 minutes - 178°
4 minutes - 175°
1 minute - 186°
2 minutes - 181°
3 minutes - 175°
4 minutes - 169°
Since I had already performed the touch test I wasn't surprised that the Bonavita lost heat faster. But I was surprised at how quickly heat was lost in both cases, and especially in the first minute, even though the surfaces were preheated. Also, this test was performed without coffee, and maybe I ought to perform that test also. I would think the temperature would drop even faster in the first few seconds as heat is transfered to the coffee as well as to the surfaces.
At any rate I've now switched back to the Clever, but I'm thinking of looking for a clean (no sludge) immersion brew method that retains heat better than either of these. Perhaps an insulated French press with a paper filter?