Is it just the curve of the cap that makes them different? That is scary if it is.
Mycology
I'm not sure if you are referring to the two images? If so, they are both pictures of the posionous Sulfur Tuft (maybe my post was confusing). The edible species has some slightly different coloring, but that's really not enough for me to be able to tell the difference with confidence.
It's easy to tell them apart. The one that kills you when you eat it is the bad one.
Just bring a friend along to help identify them
The big identification factor is that fasciculare is very bitter! I love Hypholoma lateritium and that's a trick I learned to help distinguish them.
Hmm thanks, you made me read up on the topic some more. If I come across some capnoides I think I will try and identify them with certainty! The taste is indeed a pretty fail proof factor. And actually it should even be possible to identify them visually.
I am always a little scared when leaving the relatively safe terrain of my beloved boletes.