"There are few if any reasons for continuing to use ethanol." <= I've never heard this before! All I've ever seen or heard in conversations is that things in isopropyl should be transferred to ethanol. I'm pretty sure I have seen collection proposals that used that - i.e., the fact that a portion of the collection was stored in isopropyl - as evidence of the urgency of a particular collection conservation project.

I haven't found much regarding the advantages or disadvantages of these two alcohols, but there are threads on this listserv about it. Lu referred us to this reference:
King, J. R., and S. D. Porter. "Recommendations on the use of alcohols for preservation of ant specimens (Hymenoptera, Formicidae)." Insectes Sociaux 51.2 (2004): 197-202
In which they state this one potential downside (p. 199): 

"There is evidence that long-term storage of ant specimens in 
isopropanol may discolor specimens more than ethanol (S. Cover, J. Lattke, 
pers. comm.). "

This possible downside was echoed by Michael Skvarla in that same thread. Otherwise that King and Porter paper describes these liquids as more or less equally good at preserving ants. Simmons (2015: p. 495), referring I think mainly to vertebrates, writes:

"Isopropyl alcohol (isopropanol) is also used as a preservative, although it has been
shown to cause more shrinkage of specimens than ethanol, is not as miscible in water,
and is twice as toxic as ethanol (Monick 1968). Isopropyl dissolves lipids faster than
ethyl alcohol, reacts with oxygen to form ketones and unstable peroxides, causes more
deterioration of collagen and keratin than ethanol, may be difficult to mix thoroughly,
is prone to layering, may cause softening of bone, and in low concentrations may clear
tissues (Simmons 2014). Isopropyl is typically used at concentrations of 45–70%."

Simmons, John E. "Storage in fluid preservatives." Storage of natural history collections: A preventive conservation approach 1 (1995): 161-186.

Are any collections regularly using isopropyl alcohol as a preservative?

Andy Deans
Frost Entomological Museum