I had find many had slightly confused with Agloanema species which is closely related with particular species. As for one, I would consider if it is Agloanema - there will be more red coloration on its foliage and colors included on the stem too.
Dieffenbachia however is very much grows tall and leggy, also bigger and hardy in comparison to Agloanema. Also factor is that the base dominant color is green with (white to cream tones) the difference of splashes, streaks and dots that makes the unique difference in the patterns which is somehow difficult to put in a uniform factor as each foliage is uniquely different from each other.
One thing that I seek to identify and class them according to my understanding:
The colors - some are just 2 tones and some are more than 3 tones.
I for one find that those are in 2 colored tone catagories seemed to be very stable in their appearance and also hardy.
The ones that have the shaded appearance like fades and watercolored paint wash - seemed to be more sensitive and may easily damaged and does succumb to rot.
The other factor is the hybridization and it's variety.
Technically speaking (or what I had discovered is that) Dieffenbachia seguine and Dieffenbachia maculata have similar characteristics and often crossed breed until they are most likely are of the same species.
D. maculata have unique characteristics where the leaves are more oblong shaped, sharply pointed and have fragile features in comparison to D.seguine which may be hardy and cane like.
However the D.amoena may too fall into the D.seguine category.
Here are the list Dieffenbachia (Dumbcane)
Do click on their names to get to the link to get into more detailed information
on each plant types and their characteristics.
Click on the link above for detailed information on Care & Cultivation for this plant.
These are the most common and hardy dieffenbachia often pruned and easily available even planted along roadsides and common park areas.
These 3 types have very similar behavior characteristics except for the cream marking on the foliage.
(top to below) can be considered very common types which may not be sold in nurseries anymore as they are no longer considered popular.
This one is fairly common but may not easily available in comparison to the top three above.
However - these are still considered popular due to the overall light green colors on the foliage.
I had found this one pruned and thrown away along the roadside years ago. (2009) I had not seen this grown anywhere though and even seen nurseries so far.
This was passed to be my friend and also easily able in some nurseries. These do grow big and have large foliage formation and may require space for them to grow to this size.
Dumbcane - Dieffenbachia seguine ' Tropic Rain'
Dieffenbachia 'Mayan Jade'
Dieffenbachia 'Mayan Jade'
I believe this is a recent new cultivar introduced recently in the plant market. It has a large broad foliage with tall stem stability growth and may require space to grow to this large size.
I believe these are the commonly available ones sold in nurseries now. These do hold some level of popularity due to the complex coloration and texture, though some appear to be fragile and sensitive.
Do feel free to go through and see if there is any discrepancies and if you are very sure of it's ID, do let me know as I can correct/update them. Also do share what other types of dieffenbachia that you cultivate and your experience pertaining it.