I know that heat is heat but if one type of heat is more efficient and more uniform than another, then it could result in different tasting roasts.
My guess is that since convective heat is more efficient and heats the beans more uniformly, it allows for faster fully developed roasts which would better preserve floral notes that would otherwise be lost in longer darker roasts.
Conductive heat transfer is less efficient and less uniform which is more likely to result in longer roast times and uneven roast development across the body of the bean relative to convective heat transfer.
To achieve full development at the centre of the bean, with mainly conductive heat transfer, one would probably end up with some overdevelopment at the surface of the bean. This would make it harder to preserve the delicate floral notes under these conditions.
Just my guess, but I could be wrong 
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I don’t really think that affects anything. The water molecules are heavy enough not to go upwards and around the bends to penetrate the roasting chamber, and the rest of the room is usually full of air conditioners, extraction fans and whatnot. Careful, as this is just me saying the first thing that came into my mind.
There’s no wrong in subjectivity. Radiation should be even better than convection. I have tried those IR thingies and, although they are good, colour me not impressed. There’s nothing any of those three can’t do, and the coffee will be great either way. If, in the end, you prefer one to the other, that’s completely subjective. To do a real test you should have a capable roaster, as in human, all three roasters, as in machines, and roast the same beans side by side, finishing with the same colour. But even if you do all that, the tasting part is a subjective thing by nature, so that kind of ruins everything. But if you do like it, there are fluid bed roasters to be bought at the price of a Bullet.
Completely unrelated to any of this, but related to the argument I used, which is subjectivity. Conventional and Empire (dark side) roasters, love to bring this up to justify their burned beans. Oh, you know, it’s personal preference. No, it is not, your coffee is charred. 
@braca19452f9m
This isn’t a subjective thing though, we’re talking about roasting coffee. That means there are certain things that have to happen.
You need to remove moisture and chaff, so airflow is a vital element in roasting. By its nature you need the airflow temperatures to work with the roast, and not against it. Coffee roasting is primarily about what the air is doing more than anything else.
Are you saying that the Bullet can’t do that? Are you saying that the Bullet is producing a bad cup of coffee? Are you saying that one machine roasts better than others? Are you saying drum roasters don’t do that, because drum roasters are mostly conductive with a little bit of convection? Also, how do you determine that, if not by tasting the coffee, which is subjective? The fluid bed roasters are available if you don’t like the drum. There are also roasters with direct radiation heating. Why not get those and enjoy, without trying to convert everybody? Coffee is taste, and taste is subjective. And I’m talking about taste of same colour on 3 ways of heat transfer, not between charred and normal coffee.
Bless you Barca for your passion. Nobody is suggesting that the Bullet can’t produce excellent tasting coffee. However, like any system, it does have its own characteristics and also its limitations based on its heat transfer design execution.
I use a Bullet because it is the best and most convenient 1 Kg roaster I can afford for home use and I just have to accept it’s heat transfer limitations and learn how to get the best out of it’s design philosophy.
I don’t think the difference that different heat transfer roasters can impart on coffee taste are subjective.
I can easily tell the difference in taste between coffee roasted on fluidised air bed roasters relative to traditional drum roasters. I prefer the more full bodied taste from traditional drum roasters but these also tend to have a higher level of convective heat transfer relative to the bullet design.
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Yes, the subjectiveness is the preference. Nobody said there’s no difference whatsoever. Sometimes you can taste the difference between 2 same roasts on a same machine. At least I can, but that’s also subjective. I did not see you mention the same coffee roasted on 3 different machines, just a generic fluid bed vs drum. I was talking about a controlled test in the same environment for all three and the same coffee. And why is everybody skipping radiation? The theory says it’s the best of all, as far as heat transfer goes, and you can also purchase those at decent prices. There will be a difference in taste, right? Anyway, you can buy a fluid bed roaster for pretty much the same amount of money as the Bullet. And you can buy smaller ones for half the amount. I would if I were ever blown away by how coffee roasted that way tastes. As it sits, I don’t really think a fluid bed can ever match the drum for various reasons I’m too tired to explain, and they might also be subjective. And, even if some drum roasters might get more convection than the Bullet, we’re talking small percentages. Drum will always roast using conduction as primary source of heat transfer, with some convection. So, to each his own. It’s better to save and buy something you like, even though the prices are pretty similar, than having something you’re not 100% satisfied with. Personally, I’m 120% satisfied with the Bullet, and I value your opinion very much. I also apologise that I don’t, and never will, share that opinion.
P. S. Don’t underestimate the importance of the person who controls these machines i.e. the roaster.
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@braca19452f9m
Traditional drum roastings use convection as the dominant roasting heat source.
Most machines use a variety of heat transfer because of the nature of coffee roasting. But once you get enough beans in a confined space, the air has to be moving to reduce steam, smoke, and chaff. So if you cannot avoid airflow as an important part, then you have to make sure the airflow is helping the roast.
What do you want me to say? Something like there’s no need to preheat the drum because the hot air will take care of it, as drum roasters rely on 80% convection for heat transfer? Do you want me to say there’s some problem with the Bullet’s airflow that is hindering the roast which is not attributable to the person using it? Whatever it is, you can consider it done. I concede. I agree. I surrender. And that would be it for me posting in this thread.
@braca19452f9m
Sorry if you feel like that.
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Thanks for this sincere reply.
It makes sense. And that is still in keeping with the idea of “heat is heat”. In that chemical reactions to heat will happen at certain temps, and it is just a matter of how evenly the beans have certain chemical reactions, and NOT necessarily the idea that somehow convective is somehow magical. Although, to be fair, sometimes roasting is magical. 
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Bless you Jimmy. At the end of the day I am resigned to the fact that usually it is I who is the limiting factor and never the machine or the beans I am roasting 
Haha, you know that is nonsense.
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